CODE 


Governing Industrial Lighting in 
Places of Employment 

INCLUDING 

Factories, Mills, Offices and 
Other Work Places 



1919 


Bureau of Labor, State of Oregon 
C. H. GRAM, Commissioner 







































































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Electrical Review. 


Curve of Monthly Distribution of Industrial Accidents Reported to a Large 
Accident Insurance Company and How This Is Affected by Darkness. 


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CODE 


GOVERNING 

INDUSTRIAL LIGHTING IN PLAGES 
OF EMPLOYMENT 

INCLUDING 

FACTORIES, MILLS, OFFICES 
AND OTHER WORK PLACES 



•***•*». 


Issued Under Authority of Chapter 181, 
General Laws of Oregon, 1919 

* a ** * 


1919 


BUREAU OF LABOR, STATE OF OREGON 

C. H. GRAM, Commissioner 


Salem, Oregon : 

State Printing Department 
1920 







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INDEX 


Page 

ARTIFICIAL LIGHT . 38 

Artificial light ..... . . 12 

Actual losses ..„... 31 

Determination of size of lamp to be used.. 40 

Effect on factory and mill lighting produced by modern lamps. 39 

Lighting intensities . 38 

Low ceilings ...... 40 

New lamps.....:... 38 

New possibilities . 39 

Old and new lamps ......... 38 

APPENDIX—Industrial classification, 66-70. 

CHANGING A POOR INSTALLATION . 53 

Distribution of expense .„... 53 

Using the shop force . 53 

Yearly appropriation .. 53 

DEFINITIONS .. 16 

Avoiding dark spot . 4 ....... 23 

Brightness . 18 

Classes of reflectors . 23 

Candlepower . 16 

Contrast ...:......... 19 

Eye strain ..»..... 20 

Enclosing globes . 27 

Foot candle ........ 18 

Foot candle meter . 21 

Function of reflectors ....... 22 

Glare . 19 

High intensity . 19 

Lumens . 17 

Light interiors .....:.... 23 

Measurement analogy . 17 

Mirrored glass reflectors....;. 25 

Opal reflectors ...... .. 27 

Photometer ...:. 21 

Prismatic reflectors . 26 

Reflectors and their effect on efficiency.... 22 

Shaded lamps .'... 22 

Shifting glare ............. 20 

Steel reflectors . 24 

Translucent reflector . 27 

Veiling . 19 

DISTRIBUTION OF LIGHT ON THE WORK . 48 

General lighting system, the . 48 

Keeping the lamps high . 49 

Practical case . 48 

Side light importance. 48 

Two ways to secure side light. 48 

EMERGENCY LIGHTING . 49 

Emergency lighting . 14 

GENERAL LAWS OF OREGON . 9 

GENERAL LIGHTING RULES ...-. 11 

Definitions of brightness, candle, eyestrain, footcandle, footcandle 
at floor level, footcandle at work, glare, illumination, intensity 
of, lamps, local lamps, lumen, shaded lamps, overhead lamps, 

photometer .-. 11 

General requirements.....-. 11 






















































GENERAL REQUIREMENTS . 

Artificial lighting . 

Advantages of good light . 

Actual losses .-.-. 

Effect of good light on production . 

Energy consumption a minor item . 

Interpreting the advantages of good light . 

Practical example . . . 

Value of adequate illumination . 

INTRODUCTION . 

INTRODUCTION INDUSTRIAL LIGHTING CODE .. 

MAINTENANCE .-. 

Lamps ... 

Maintenance .-.-. 

Marking columns . 

Method of washing . 

Method of inspection and maintenance. 

Noting soiled reflectors . 

Overhead system . 

Windows . 

MEASUREMENTS ... 

Brightness measurements . 

Standard instrument for measurement . 

Standard instrument .:. 

NATURAL LIGHT (Daylight) . 

Bench location . 

Classification . 

Dirt accumulation .. 

Importance of daylight . 

Increasing the value of floor space . 

Prism glass ... 

Skylights .... 

Skylights, monitor construction . 

Skylights, saw-tooth construction . 

Sunshine, w T hen not desirable. 

Tempering the light . 

Upper portion of the windows. 

Window glasses . 

Wire glass .. 

Wire glass as safeguard . 

Wide aisles .. 

Varying conditions . 

SHADING OF LAMPS FOR OVERHEAD LIGHTING 

SHADING OF LAMPS FOR LOCAL LIGHTING . 

SWITCHING AND CONTROL APPARATUS . 

Control of lamps and arrangement of switches. 

Control parallel to windows . 

Locating switches and control . 

Practical case . 

TABLES— 

Table 1—Illumination intensity (footcandles) . 

Table 2—Wattage per squard foot . 


29 

29 

30 

31 
30 
30 

30 

31 
30 



16 

51 

51 

15 

51 

53 

51 

51 

51 

51 

45 

46 

45 

13 

31 

34 

32 
38 
31 

33 

35 
35 
35 

37 

38 

34 

34 

35 
35 
38 
33 
33 

46 


50 

50 

50 

50 


12 

45 
























































INTRODUCTION 


In the future, even more than in the past, the need of conserving the 
human element will be necessary. There are many reasons for this condi¬ 
tion, such as the restricted supply of labor, high wages, high cost of 
material and keen competition in the world market. All of these will 
appeal to the employer directly and will cause him to take steps himself 
to protect the laborer in his plant. Of even greater importance, however, 
is the humanitarian side, the saving of human lives, the prevention of 
human wrecks and the improvement in human comfort and contentment; 
but because these factors do not seem to be so directly connected with the 
cost of production the average employer gives less attention to them, 
although in the end he pays a high price for this neglect. However, the 
fruit of this negligence does not fall alone upon the employer but the state 
must bear a large proportion of this cost directly in the form of pensions, 
compensation, and the maintenance of institutions for cripples and other 
dependents; and indirectly in the loss of the productive, and the increase 
of the dependent element of its production. 

This state has endeavored in the past to improve conditions by estab¬ 
lishing a Bureau of Labor with its corps of inspectors as well as an 
Industrial Accident Commission. It has been shown by careful investiga¬ 
tion in recent years that not less than 20 per cent of the preventable 
accidents are due, either directly or indirectly, to improper illumination. 
The 1919 legislature of the state of Oregon therefore took one more 
important step toward the prevention of unnecessary accidents by providing 
for proper general and emergency lighting, both natural and artificial, 
in all places of employment. 

In presenting this bulletin to the public, acknowledgment is due to 
the Illuminating Engineering Society for the work it has done in pioneer¬ 
ing the way for industrial lighting codes and to certain of its members 
individually for very material help in assisting the state of Oregon to 
secure suitable legislation along this line, especially is this true of the 
assistance rendered by Mr. L. B. Marks, chairman of the divisional lighting 
committee, a subdivision of the Advisory Council of National Defense. 

Particular reference is made to the Code of Lighting—Factories, Mills 
and Other Work Places—prepared by the Industrial Lighting Code Com¬ 
mittee and published in 1915. Much of the subject matter of this bulletin 
has been taken from that code and used verbatim, such additional notes 
and rearrangements being made as were deemed more suitable to local 
conditions. Credit is also due to the industrial commissions of New York, 
New Jersey, Pennsylvania, Ohio, Wisconsin and California and to the 
engineering department of the National Lamp Works of the General 
Electric Company for helpful suggestions obtained from their lighting 
bulletins, as well as to the Edison Lamp Works, the National Lamp Works 
and the Ivanhoe-Regent Works of the General Electric Company; the 
X-Ray Reflector Company, the Holophane Glass Company, the Wisconsin 
Industrial Commission, and the Illuminating Engineering Society for many 
illustrations used in this bulletin. 

In accordance with Section 8, Chapter 181, General Laws of Oregon, 
1919, the Commissioner of Labor of the state of Oregon appointed a 
Lighting Commission consisting of three persons. This commission, after 

7 


8 


LIGHTING IN PLACES OF EMPLOYMENT 


holding many meetings and with the active and valuable assistance of the 
Commissioner of Labor, presents herewith its report in the form of a 
lighting bulletin, embracing the legislative act, together with the lightin 
rules determined by the commission and their explanatory notes formin 
an appendix to these rules. 

LIGHTING COMMISSION, 

Y. H. Haybarker, 

F. C. Knapp, Chairman, 

F. H. Murphy, Secretary. 






LIGHTING IN PLACES OF EMPLOYMENT 


9 


PART I—INDUSTRIAL LIGHTING CODE 


GENERAL LAWS OF OREGON FOR 1919 

[Effective May 29, 1919] 


CHAPTER 181 


AN ACT 

[H. B. 186] 

To require owners, lessees and operators of places of employment to provide 
emergency and general natural and artificial lighting; defining how the 
minimum of light shall be established ; requiring the commissioner of labor 
and inspector of factories and workshops to enforce the same ; and providing 
a penalty for failure to comply with the provisions of this act. 

Be It Enacted by the People of the State of Oregon: 

Section 1. The following terms, as used in the various sections of this 
act, shall be construed as follows: 

(a) The phrase “place of employment” shall mean and include every 
place, whether indoors or out, or underground, and the premises appur¬ 
tenant thereto, where either temporarily or permanently any industry, 
trade or business is carried on, or where any process or operation, directly 
or indirectly relating to any industry, trade or business is carried on, and 
where any person is directly or indirectly employed by another for direct 
or indirect gain or profit, but shall not include any place where persons 
are employed in private domestic service or agricultural pursuits which 
do not involve the use of mechanical power. 

(b) The term “owner” shall mean and include every person, firm, cor¬ 
poration, state, county, town, city, village, manager, representative, officer 
or other person having ownership, control or custody of any place of 
employment or of the construction, repair or maintenance of the buildings 
of any such place of employment or who prepares the plans for the 
construction of any place of employment. 

Section 2. All passageways and other portions of places of employment, 
and all moving parts of machinery which are not so guarded as to prevent 
accidents, where, on or about which persons work or pass or may have to 
work or pass in emergencies, shall be kept properly and sufficiently lighted 
during working hours. The halls and stairs leading to the workrooms 
shall be properly and adequately lighted, and a proper and adequate light 
shall be kept burning by the owner or lessee in the public hallways near 
the stairs, upon the entrance floor and upon the other floors on every 
workday in the year, from the time when the building is open for use in 
the morning until the time it is closed in the evening, except in times 
when the influx of natural light shall make artificial light unnecessary. 
Such lights shall be so arranged as to insure their reliable operation when 
through accident or other cause the regular factory or workshop lighting 
is extinguished. 

Section 3. All workrooms in any place of employment shall be properly 
and adequately lighted during working hours. Artificial illuminants in 
every workroom .shall be installed, arranged arid used so that the light 
furnished will at all times be sufficient and adequate for the work carried 
on therein, and so as to prevent unnecessary strain on the vision, or glare 
in the eyes of the workers. 



10 


LIGHTING IN PLACES OF EMPLOYMENT 


Section 4. Working or traversed spaces in all places of employment 
as defined in this act shall be supplied during the time of use with artificial 
light in accordance with a schedule of minimum values which shall be 
determined as hereinafter specified, and when the natural light is less than 
the intensity so determined, the artificial light must be used. 

Section 5. Lamps must be so located or suitably shaded as to minimize 

glare. 

Section 6. All lamps and lighting appliances must be so installed in 
regard to height, spacing, reflectors or other accessories as to secure a 
good distribution of light on the work, avoiding objectionable shadows and 
sharp contrasts of intensity. Emergency lamps shall be provided in the 
main aisles and in all stairways, passageways and exits so as to afford 
sufficient guidance to provide the safe exit from said places of employment 
in case of emergency. Such lamps shall be in operation concurrently with 
the lighting and independent thereof. 

Section 7. The switching and controlling apparatus shall be so placed 
that at least pilot or night lights may be turned on at the main points 
of entrance. 

Section 8. The Commissioner of Labor and Inspector of Factories and 
Workshops of the state of Oregon is hereby authorized to establish certain 
minimum values for lighting, which shall be deemed proper and adequate 
in accordance with the conditions set forth in this act. In arriving at what 
values shall be used in this schedule of minimum lighting, and such other 
rules as shall determine definitely what shall constitute compliance with 
the provisions of this act, he shall be guided by the best engineering 
practice as set forth in the recommendations of the “Illuminating Engineer¬ 
ing Society.” Before such schedule and rules, however, shall become 
effective, the Commissioner of Labor must, upon his own motion, appoint 
a commission of three persons, one to represent the manufacturing interests, 
one to represent the operating electrical workers, and one must be an 
electrical engineer. Notice of the public meetings of such commission 
shall be published in the leading newspapers of each county in the state, 
giving the time, place and purpose of such meetings. The commission 
shall have power, after holding these public meetings, to establish, to 
rearrange or to readjust the schedule of lighting values and rules as 
above set forth. These rulings or readjustments shall then become effective, 
thirty days after they have been made, and the Commissioner of Labor 
shall serve notice, in writing or by publication in the leading newspapers 
of each county in the state, of the rulings thus made and of the date upon 
which they become effective. 

Section 9. Any person, firm or corporation who violates or does not 
comply with the provisions of this act or who shall fail or neglect to 
provide the necessary and proper illumination herein provided, within 
thirty (30) days after receiving written notice so to do by the Commissioner 
of Labor and Inspector of Factories and Workshops, is guilty of a misde¬ 
meanor, and upon conviction shall be punished by a fine not exceeding the 
sum of fifty dollars ($50), and that for the purposes of this act each day 
that such violation continues, or for each day such refusal continues, 
shall constitute a separate and distinct violation of this act. 

Filed in the office of the secretary of state February 27, 1919. 




LIGHTING IN PLACES OF EMPLOYMENT 


11 


GENERAL LIGHTING RULES 

Determined in accordance with Section 8, Chapter 181, 
of the General Laws of Oregon for 1919 

Rule 1. Definitions 

(a) Brightness means the intensity of light per unit area emitted from, 
or reflected by, a body; and in these rules is expressed in candlepower 
per square inch. 

(b) Candle (or candlepower) means the unit of luminous intensity 
maintained by the national laboratories of the United States, France, and 
Great Britain. 

(c) Eyestrain means a physiological condition of the eye resulting in 
discomfort, poor vision, or fatigue. 

(d) Foot-candle means the unit of illumination equal to one lumen 
per square foot. It is the lighting effect produced upon an object by a 
lamp of one candlepower at a distance of one foot. 

(e) Foot-candles at floor level means the intensity of illumination on 
the floor of the space specified. 

(f) Foot-candles at the work means the intensity of illumination on the 
object upon which work is being performed. 

(g) Glare means any brightness within the field of vision of such a 
character as to cause discomfort, annoyance, interference with vision, or 
eye fatigue. 

(h) Illumination means the quantity of light thrown upon an object 
by a luminous body; it is usually measured in foot-candles. 

(i) Intensity of illumination means the number of foot-candles per 
square foot of area. 

(j) Lamp means that part of the lighting equipment from which the 
light originates. 

(k) Local lamps (or lighting) means lighting units located close to 
the work, and intended to illuminate only a limited area about the work. 

(l) Lumen means the unit of luminous flux or light output and is the 
quantity of light necessary to produce an average intensity of illumination 
of one foot-candle over an area of one square foot. 

(m) Shaded means that the lamp is equipped with a reflector, shade, 
enclosing globe, or other accessory for reducing the brightness in certain 
directions, or otherwise altering or changing the distribution of light from 
the lamp. 

(n) Overhead lamps (or lighting) means lighting units installed above 
ordinary head-level to secure a general illumination over a considerable 
area. 

(o) Photometer means a standardized instrument suitable for making 
illumination measurements. 

Rule 2. General Requirements 

(a) Working or traversed spaces in buildings or grounds of places of 
employment shall be supplied during the time of use, with either natural 
or artificial light in accordance with the following rules (3-11). 



12 


LIGHTING IN PLACES OF EMPLOYMENT 


Rule 3. Natural Light 

(a) Windows, skylights, or other roof-lighting construction of buildings 
shall be arranged with the glass area so apportioned that at the darkest 
part of any working space, when normal exterior daylight conditions obtain 
(sky brightness of 1.50 candlepower per square inch), there will be avail¬ 
able a minimum intensity equal to twice that of rule 4, otherwise artificial 
light of intensities specified in rule 4 shall be provided. 

(b) Awnings, shades, diffusive or refractive window glass shall be 
used for the purpose of improving daylight conditions or for the avoidance 
of eyestrain wherever the location of the work is such that the worker 
must face large window areas through which excessively bright light may 
at times enter the building. 

Note.—The intensity requirements for adequate day lighting are much 
higher than those for adequate night lighting, because in general under 
daylight conditions the light reaching the eye from all surroundings in the 
field of vision is much brighter than at night, and hence a correspondingly 
more intense light must fall on the object viewed. 

Rule 4. Artificial Light 

(a) When the natural light is less than twice the minimum permissible 
intensities of illumination set forth in the following table, artificial light 
shall be supplied and maintained in accordance with the table. The 

intensities of ordinary practice indicate the desirable illumination for 
best working conditions. 


TABLE I 


ILLUMINATION INTENSITY AT THE WORK IN FOOT-CANDLES 


(a) Roadways and yard thoroughfares. 

(b) Storage spaces . 

(c) Stairways, passageways, aisles . 

(d) General lighting for workrooms . 

(e) Toilets, washrooms, water closets, dressing 

rooms and elevator cars . 

(f) Rough manufacturing, such as rough 

machining, rough assembling, rough 
bench work, foundry floor work . 

(g) Fine manufacturing, such as fine lathe 

work, pattern and tool making, light 
colored textiles ... 

(h) Office work, such as accounting, type¬ 

writing, etc... 

(i) Special cases of fine work, such as watch 

making, engraving, drafting, dark 
colored textiles ... 



(Recommended 

Minimum 

Values) 

Permissible 

Ordinary 

Intensity 

Practice 

0.02 (1/50) 

0.05- 0.25 

0.25 (%) 

0.5 - 1 

0.25 (%) 

0.75- 2 

0.5 (%) 

1.0 - 2 

1.0 

1.5 - 3 


2 


3 - 6 


3 

3 


4 - 8 
4 - 8 


5 


10 -15 


Note 1.—Some exceptions to the intensity rule: 


(a) There are some operations that are performed in comparative 
darkness, as for example, photographic processes in the dark room. 

(b) There are some operations that are best observed by their own 
light, as in parts of the process of working glass. 

(c) Some operations are best observed by the “silhouette” method of 
lighting in which the work is seen against a lighted background in a 
comparatively dark room, as in some processes of working with dark 
threads and lamp filaments. 












LIGHTING IN PLACES OF EMPLOYMENT 


13 


In all such cases in which work is of necessity carried on in comparative 
darkness, special precautions should be taken to properly safeguard the 
workmen. 

Note 2.—The minimum foot-candles specify the lowest illumination 
intensity with which the employes can be expected to work with safety 
when artificial light is used. It is to the advantage of the employer to 
provide the intensities of ordinary practice, as this results in less eye 
strain, greater accuracy of workmanship, increased production for the 
same labor cost, less spoilage. When part daylight and part artificial 
illumination must be used together, it is desirable to employ even higher 
intensities than those of ordinary practice in the table above. (See note 
accompanying rule 3.) . 

In order that the illumination intensities will never fall below the 
minimum during the interval between inspections installations should be 
designed to produce initial values at least 25 per cent higher. 

Rule 5. Measurements 

(a) For the purpose of light measurements, a standardized photometer, 
certified by the Labor Commissioner of the state of Oregon, shall be used, 
and such measurements shall be made at the locations specified by these 
rules. 


Rule 6. Shading of Lamps for Overhead Lighting 


(a) Lamps suspended at elevations above eye level less than one-quarter 
their distance from any positions at which work is performed, must be 
shaded in such a manner that the intensity of the brightest square inch 
of visible light source shall not exceed seventy-five candlepower. 

Note.—The following diagram illustrates the application of the above 
rule, the distance being explanatory and representing the ratio between 
the height of the lamp above the eye level and its horizontal distance 
from the eye. 


CP/UNG L/NP-+ 




l amps Mow the limit here 
shown must he so shaded 
that the Cdnd/e power 
of the brightest -5%. // 7 . 

of the L ight Source 
shaft not exceed 7 S 






P7os f distant 
/amp from art a 
Po)nt at which 

trork is 
formed- 



yi Limited Height i\ 
^ of Mounting. *' 


PND or ROOM 

PND OP /ZOOM 

pioo/e iPVPL y 


Fig. 1.—Illustrating Rule No. 6. 


Exception.—Lamps suspended at elevations greater than twenty feet 
above the floor are not subject to this requirement. 












14 


LIGHTING IN PLACES OF EMPLOYMENT 


Note 1.—Glare from lamps or unduly bright surfaces produces eye strain 
and increases the accident hazard. The brightness limit specified in this 
rule is an absolute maximum. Very much lower brightness limits are 
necessary in many interiors illuminated by overhead lamps, if the illumina¬ 
tion is to be satisfactory. In some cases the maximum brightness should 
not exceed that of the sky (two to three candlepower per square inch). 

Note 2.—Where the principal work is done on polished surfaces, such 
as polished metal, celluloid, varnished wood, etc., it is desirable to limit 
the brightness of the lamps in all downward directions to the amount 
specified in this rule. 

Note 3.—For method of measuring brightness, see Section 5 of Part II. 

Rule 7. Shading of Lamps for Local Lighting 

(a) Lamps for local lighting must be shaded in such a manner that 
the intensity of the brightest square inch presented to view from any 
position at which work is performed, shall not exceed three candlepower. 

Note.—In the case of lamps used for local lighting, at or near eye 
level, the limits of permissible brightness are much lower than for lamps 
used for overhead lighting, because the eyes are more sensitive to strong 
light received from below, and because such light sources are more 
constantly in the field of view. 

Rule 8. Distribution of Light on the Work. 

(a) The reflectors or other accessories, mounting heights, and spacing* 
employed with lamps shall be such as to secure a reasonably uniform dis¬ 
tribution of illumination, avoiding objectional shadows and sharp con¬ 
trasts of brightness. If local lighting is used, there shall be employed in 
addition a moderate intensity of overhead lighting, with a minimum of 
not less than one-half ( y 2 ) foot-candle. 

Exception.—Where the light from the local lamps falls principally upon 
surfaces which are white or nearly so, and the ceilings and walls of the 
rooms are light, there is often a sufficient general illumination received 
indirectly by reflection to obviate the necessity of additional overhead 
lighting. 

Note.—When local lighting is used as the sole source of illumination 
of an interior, the field of illumination from each lamp is in contrast to 
the surrounding darkness, thereby causing eyestrain and increasing the 
accident hazard. 

Rule 9. Emergency Lighting 

(a) Emergency lights shall be provided in all work space aisles, stair¬ 
ways and passageways; at all exits, and on all outside landings of fire- 
escapes or other structures used as regular or emergency means of egress 
to provide for reliable operation when, through accident or other cause, 
the regular lighting is extinguished. 

Note 1. It is the intention of the rule to guard against accident due 
to the failure of the regular lighting system, by providing sufficient 
illumination to enable the occupants to: 

(a) Avoid contact with moving machinery and other danger points 
until the regular lighting is again placed in operation. 

(b) To vacate the building safely and expeditiously when this is 
necessary because of fire or other causes. 



LIGHTING IN PLACES OF EMPLOYMENT 


15 


Note 2.—Emergency lighting may be installed in various ways. The 
method to be employed depends upon the size of the premises, the extent 
of the hazards of employment, and the means' available for supplying such 
emergency lighting. 

(b) Emergency lighting systems, including all supply and branch lines, 
shall be entirely independent of the regular lighting system and shall be 
lighted concurrently with the regular lighting system and remain lighted 
throughout the period of the day during which artificial light is required 
or used. 

(c) Emergency lighting, where required, shall have a minimum intensity 
of one-fourth i 1 /^) foot-candle. 

(d) Emergency lighting systems shall, where the nature of the hazard 
is such as to require it, be supplied from a source independent of the 
regular lighting system wherever possible. This source of supply and con¬ 
trolling equipment shall be such as to insure the reliable operation of the 
emergency lighting system when, through accident or other cause, the 
regular lighting system is extinguished. Where a separate source of supply 
can not be obtained for the emergency lighting, the feed for emergency 
lights must be taken from a point on the street side of the service equip¬ 
ment. Where source of supply for the regular lighting system is an 
isolated plant within the premises, an auxiliary lighting system of suffi¬ 
cient capacity to supply all emergency lighting must be installed from 
some other source, or suitable storage battery; or separate generating unit 
may be considered the equivalent of such service. 

Rule 10. Switching and Control Apparatus 

(a) Switches or other controlling apparatus shall be so installed that 
pilot or night lights may be controlled from the main points of entrance. 
Pilot or night lights may be a part of the emergency lighting system. 

(b) All switching and control apparatus on emergency pilot and night 
lights shall be plainly labeled for identification. 

Note.—The purpose of the rule is to make it possible for the night 
watchman or other qualified persons to turn on enough lamps, when enter¬ 
ing any portion of the premises at night, to enable them to safely see their 
way around without the need of a lantern or flashlight. 

Rule 11. Maintenance 

All lighting equipment and windows shall be periodically cleaned, in¬ 
spected, kept in order and when defective, replaced, so that the intensities 
of illumination will never fall below those specified in rule 4. 



16 


LIGHTING IN PLACES OF EMPLOYMENT 


PART II—EXPLANATION OF THE PROVISIONS OF THE 
INDUSTRIAL LIGHTING CODE 

INTRODUCTION 

In order that compliance with this code may be easily and readily 
accomplished it has been deemed advisable to prepare the following explana¬ 
tion of the rules and discussion of such other points as are pertinent thereto. 
This is, however, in no way to be considered as a treatise on illumination. 
It considers the subject only in a very brief and elementary manner in 
an endeavor to provide a clear understanding of the code rules and to 
enable some of the simpler cases of illumination to be worked out by 
the inexperienced engineer where no illuminating engineers are available. 

It is believed, however, that the interests of employer and employe 
alike will be best served by employing the services of an experienced 
illuminating engineer whenever such a specialist is available, in the same 
way that it is necessary and advisable to employ an architect to plan a 
building or an engineer to design a bridge. 

“When adequate and satisfactory illumination is substituted for the 
all too prevalent poor illumination in factories, mills and other work places, 
the results obtained are mutually beneficial to the employes, the employers 
and the country as a whole. Under proper illumination conditions, the 
health, contentedness, safety and skill of the employes are maintained at 
a high standard, the output is increased in quantity and improved in 
quality, while there is a proportional reduction in the cost of each unit of 
finished product when it reaches the public. 

“While it is desirable to have adequate light over the working areas, 
it is absolutely essential for the proper results to eliminate or minimize 
the light which otherwise would pass directly from the lamps to the eyes 
of the workers; that is, one must avoid glare, which is not only fatiguing 
to the eye but also conducive to the incorrect estimation of sizes and 
locations of objects in the field of view.” 

Code of Lighting, Divisional Committee on Lighting. 

SECTION I.—DEFINITIONS 

The definitions given are, for the most part, self-explanatory but a 
brief explanation of a few of the terms which may not be altogether 
familiar to the average layman will not be amiss. 

Candle Power 

The term “candle,” or “candle power,” is the oldest unit used in con¬ 
nection with illumination. Its use is probably due to the fact that at the 
time better types of light sources began to be used candles were the 
almost universal illuminants and further their sizes and materials were 
so nearly the same that it could be said roughly that they gave the same 
amount of illumination, hence the comparison of the new lamp as being 
equivalent to so many candles. It is quite probable that the first com¬ 
parisons were made by placing the candles and the new light source side 
by side and making a rough comparison with the eye. This naturally led 
to the method of measuring lamps or light sources by means of the 
intensity of light given out in a horizontal direction and this was continued 




LIGHTING IN PLACES OF EMPLOYMENT 


17 


until comparatively recent times. Meanwhile methods of determining what 
should constitute a standard candle power as well as of making accurate 
comparisons of the intensities between two different types of light sources 
have been perfected. 

The methods of determining the value of a light source by the intensity 
of light given out in a horizontal direction could only be satisfactory if 
all light sources gave out the same relative amount of light always in the 
same direction. As a matter of fact no practical light source gives out 
the same intensity of light in every direction from its center, and further 
the different types of modern light sources do not distribute their light 
in the same manner from their centers, some give more light in the hori¬ 
zontal direction than in other directions, others give the most light in 
a downward direction, while still others give a maximum amount of light 
in some direction between these two extremes. It is therefore apparent 
that some other means than the measurement of lioriztontal intensity 
must be used in order to get any satisfactory comparison of the relative 
amount of light given out by various light sources. Futliermore since the 
measure of the ability of the light source to illuminate a room is dependent, 
not upon the intensity of light given out in the horizontal or in any other 
single direction, but upon the total amount of light emitted by the lamp, it 
is essential that some unit be adopted which will be a measure of the 
total output. 

These conditions have been met by the development of an instrument for 
measuring the light output of lamps and they will hereafter be rated by the 
output in lumens, eventually dropping the meaningless term “horizontal 
candle power.” 

Lumens 

The new unit by which the total amount of light output is indicated is 
called the “lumen.” To return to our original source the “candle” we 
may state that the standard three-quarter inch candle will give out a total 
amount of lighting approximately equal to ten lumens and a 40 watt 
Mazda lamp will emit approximately 370 lumens. 

To further explain these two units, i. e., the candle power and the 
lumen, a measurement analogy is given in bulletin No. 7-C, Fundamentals 
of Illumination and Design, published by the engineering department of 
the National Lamp Works of the General Electric Company, which is 
hereby quoted: 

A Measurement Analogy 

“A conception of the relations just discussed may be obtained from the 
following simple analogy: Suppose that we have a pool of water of 
unknown depth, whose area has been found to be 5,000 square inches, and 
it is desired to obtain a measurement of the quantity of water in the 
pool, At first thought, one might be tempted to measure the depth at some 
point by means of a yardstick. If, for example, the depth at this point 
were found to be six inches, he might say that the pool contained six 
inches of water. Obviously, such a measurement would be practically 
useless. A measurement of this sort corresponds to the measurement of 
the quantity of light given off by an illuminant as determined by its candle 
powder in a single direction. On second thought, the investigator might make 
determinations of depth at regular intervals along a straight line through 



18 


LIGHTING IN PLACES OF EMPLOYMENT 


the center of the pool from edge to edge and find the average depth along 
this line to be, say four inches. To say that the pool contains four inches 
of water would hardly be more conclusive than the first determination. 
Such a measurement would correspond to the mean horizontal candle power 
of a light source. If the surface of the pool were divided into a large 
number of equal squares and measurements of depth made at the center of 
each square, the average depth thus found would give a definite idea of 
the quantity of the water in the pool since the surface area is already 
known. This determination corresponds to mean spherical candle power. 
Now, if the average depth of the pool as just determined, is, say four and 
one-half inches, the quantity of water in the pool is four and one-half 
times 5,000, or 22,500 cubic inches. To say that the pool contains 22,500 
cubic inches of water is definite and positive, and this measurement cor¬ 
responds to the number of lumens given off by a light source. The average 
depth of the pool corresponds in this analogy to the average intensity of 
the light source in all directions and the area of the pool corresponds to 
the area of the imaginary sphere about the light source.” 


Foot Candle 


A foot candle is the unit used to measure the intensity of illumination 
falling upon or received by a given surface. If a quantity of light equal to 
one lumen falls uniformly over a surface having an area of one square foot 
the intensity of illumination will be one foot candle. If this same quantity 
of light should be uniformly distributed over an area of two square feet 
the intensity of illumination would be only one-half of a foot candle. To 
further illustrate this another measurement analogy will be used. Let 
use suppose that one hundred and forty-four cubic inches of chalk dust 
be spread uniformly over a flat surface of one square foot of area, the 
depth of the dust will be one inch, comparable to the illumination intensity 
of one foot candle. Now suppose that the same quantity of chalk dust be 
spread uniformly over a flat surface of two square feet in area, the depth 
of dust will be only one-half inch, this time comparable to the illumination 
intensity of one-half foot candle. 

A working idea of the value of a foot candle of illumination may he 
obtained by considering the intensity on a newspaper being read by the 
light of a candle, the paper being held approximately one foot away from 
the candle. If the paper is held two feet from the candle the intensity of 
illumination would be approximately one-fourth foot candle. 

Brightness 


The brightness of an object is measured by the amount of light given off 
by it per unit of area.* “Care should be taken to avoid confusing the 
intensity of illumination falling on a surface as indicated by the foot 
candles with the appearance as regards brightness on a surface. A gray 
surface lighted to an intensity of one foot candle will not appear so bright 
as a white one for a greater proportion of the light falling upon the plane 
is absorbed and lost. The brightness of an object depends upon the 
intensity of illumination on it and the percentage of light that it reflects ” 

wh.V h .! 88 «; ay r b v°. determined fOT the lamp filament or the mantle in 
which case the light measured originates in and is emitted by the surface, 

mem CompaSy neering Depart - 




LIGHTING IN PLACES OF EMPLOYMENT 


19 


or it may be determined for the bowl of the semi-indirect lighting fixtures 
in which case it is a measure of the light which is transmitted through the 
glass, finally it may be determined for a reflecting surface such as the 
ceiling, the wall, or the work upon which light falls and is reflected back, 
in which case the brightness is a measure of the amount of light reflected 
from such a surface. In all cases it is a measure of the amount of light 
coming from each unit area of the surface considered. As a matter of 
convenience in the size of the unit the square inch has been selected as the 
unit of area, while the unit of light intensity is, of course, the candle power, 
thus we have the candle power per square inch as the unit used to measure 
the brightness of a surface. 

Glare 

Glare is sometimes referred to as “light out of place.” Its effects may 
be caused not only by the light reaching the eye directly from the sources 
having a brightness greatly in excess of that of the objects viewed, but they 
may be produced by excessive reflections from the objects within view. 

Since glare is of common occurrence and since its effects are so serious 
a short discussion of the subject is felt advisable. The subject will be 
divided under four heads, high intensity, contrast, veiling, and shifting 
glare. 

High Intensity. —High intensity or brightness glare is due to excessive 
brightness within the field of view. This may be due to a bare lamp, to 
an enclosing globe of insufficient area, to a portion of a reflector of insuf¬ 
ficient area, etc., that is so located that the eye must face it in the normal 
routine of work. The obvious remedy is to change the location of the 
lamp, use a larger enclosing globe or a proper reflector, etc., as the case 
may be. 

Contrast. —Contrast glare is due to a bright surface in proximity to a 
relatively dark surface. The bright area might be entirely comfortable to 
the view if the surroundings were light colored but with dark surroundings 
the eye endeavors to accommodate itself to both bright and dark areas 
with resulting fatigue. A system of local lighting frequently produces such 
a condition. With local lighting the light falls within a very restricted 
area on and about the work frequently lighting the work itself to a very 
high intensity while the surroundings and upper parts of the room are very 
dark. This is a serious condition and can be remedied by providing some 
general illumination from lamps located near the ceiling. Painting the 
ceiling and upper walls and machinery some light color also will assist 
in eliminating this condition of glare. 

Veiling. —Veiling glare is the result of the reflection of a light source 
or other bright object in a polished surface upon which work is being done. 
It produces the effect of a thin veil of light over the work making it diffi¬ 
cult to distinguish outlines clearly. This is a very serious form of glare 
if the worker must continually face it. It is frequently encountered where 
work must be done on calendared or glossy paper or on polished surfaces 
of wood or metal, etc. It can some times be remedied by a greater diffusion 
of the light from the light source, by changing the direction or angle of 
the light upon the working surface, or in the case of glossy paper by 
changing to a grade of paper with more of a mat surface. 



20 


LIGHTING IN PLACES OF EMPLOYMENT 


Shifting.—Shifting glare is the name given to what is more correctly 
known as “flicker glare.” The term “shifting” has been used in this case 
because it was thought that such a name might convey somewhat more 
readily the nature of the trouble. Such a condition results from the rapid 
shifting of alternate bright and dark areas across the field of view. This 
causes the eye to become fatigued in an endeavor to accommodate itself to 
the constantly changing field of light intensity. Such a condition would 
exist where a bright light source was so located that its light was directed 
through an open framework so as to cast deep shadows in the field of 
view. If both light source and framework were stationary it might present 
a case of contrast glare but if either the light source or the framework 
were subject to movement back and forth even though the intensity differ¬ 
ences may not be extreme enough to produce serious contrast glare when 
stationary, yet the shifting of these bright and dark areas will cause a 
very annoying and often serious shifting or flicker glare. The obvious 
remedy is to prevent the movement of either the light source or the frame¬ 
work or better still to relocate the light source so as to eliminate the 
shadows at all times. 

“In factory lighting each lamp should be so located that the eye does 
not see it in the ordinary course of work, and so shaded or covered that 
brilliant reflections are avoided. The desired results can be obtained by 
putting over the lamp an open shade which screens it and reflects down¬ 
ward much of the light which would otherwise be either of no value or 
actually detrimental. Another way of accomplishing the same result is 
to surround the lamp with a diffusing globe dense enough not to reveal 
the form of the actual light source within, but to give the effect of the 
light pouring from the globe as a whole.” 

The above discussion on glare is given because of the very great 
importance of the subject. There is no question that if the various forms 
of glare could all be eliminated it would mark one of the greatest single 
steps that could be taken toward the preservation of eyesight, the improve¬ 
ment of shop morale, the decrease in accidents, and the reduction of unit 
cost in producing work. 


Eye Strain.—Eye strain is defined as the physiological condition of the 
eye resulting in discomfort, poor vision, or fatigue. It is the cause of 
headaches, nervousness, inaccuracy, inattention to work and decreased 
speed. It may be caused from many conditions but so far as the field 
of illumination is concerned there are two principal causes, i. e., insufficient 
illumination and glare. 

The subject of glare has already been considered and insufficient 
illumination is cared for under rules 3 and 4. The rules, however require 
only sufficient illumination to reduce accidents and such intensities are 
not sufficient to necessarily prevent eye strain. The recommended-values 
represent more nearly what should be used for such purposes and that 
is one of the reasons for including them in this code. 

Care is urged on the part of those responsible for the health and 
welfare of employes to see that adequate eye protection is afforded in all 
operations which are apt to cause injury to eyesight if such protection 
is neglected. As typical of such other causes of danger to eyesight arc 
welding may be mentioned, where the operator, according to accepted 
practice, must wear a helmet serving as an eye shield as well as a shield 



LIGHTING IN PLACES OF EMPLOYMENT 


21 


for the face and head in general. Protective glasses for this purpose 
should not be judged as to their protective properties by mere visual inspec¬ 
tion, they should, however, be analyzed for their specular transmission of 
invisible radiation. Protective measures should also be taken to prevent 
on-lookers from being unduly exposed to such eye dangers, by enclosing 
the welding operations with suitable partitions. These general remarks 
apply with equal force from the standpoint of those handling the operations 
to such other cases as testing of arc lamps, inspection of hot metal, and 
similar cases.” 


Photometers. —A photometer is an instrument used for the purpose of 
determining either the intensity of light in candle power or the intensity 
of illumination in foot candles. At first such a device was a labora¬ 
tory instrument but later successful portable instruments were developed 
with a very high degree of accuracy. These, however, were too expensive 
and too technical in their operations to be of great value to the layman. 
It has only been within the past two or three years that an instrument 
inexpensive enough and simple enough in operation for general use has 
been available. This instrument is described in the two following para¬ 
graphs taken from Bulletin No. 36, issued by the Engineering Department 
of National Lamp Works of General Electric Company, entitled “Foot- 
Candle Meter.” 



' Fig - . 2.—Foot-candle Meter. 

Foot-Candle Meter. —“An instrument called the foot-candle meter has 
recently been designed to measure foot-candle intensities quickly and with 
a fair degree of accuracy. It is very simple in operation, so light, that 
it can be easily carried about, and so small that readings can be taken 
in very restricted space. The instrument is shown in Figure 2. In 
operation, it is placed upon or adjacent to the surface on which a measure¬ 
ment of the foot-candle intensity is desired. A lamp within the box illu¬ 
minates the under side of the screen to a much higher intensity at one end 
than at the other. The illumination which it is desired to measure is, of 
course, practically uniform over the entire scale. Closely spaced translu¬ 
cent dots, which serve the same purpose as the grease spot in the simple 










22 


LIGHTING IN PLACES OF EMPLOYMENT 


bar photometer, line the scale from end to end. If the illumination on the 
scale from the outside falls within the measuring limits of the meter 
(0.05-25 foot-candles) the spots will appear brighter at one end of' the 
scale than at the other, and at the point where the spots are neither brighter 
nor darker than the white paper scale the illuminations from within and 
from without are equal. The scale is accurately calibrated with the lamp 
within the box burning at a certain definite voltage. A voltmeter and reho- 
stat permit the operator to adjust the lamp voltage to that at which the 
instrument was originally calibrated. The energy is supplied from small 
dry cells. 

“This instrument is proving very serviceable for ‘checking up’ installa¬ 
tions to insure, for example, that the illumination is ample when the 
lighting equipment is in first-class shape and to see that it is not allowed 
to fall below a desirable value due to improper care and attention being 
given to the lighting system.” 

Shaded Lamps. —The term “shaded” as used in these rules has a very 
general meaning. It refers to any device used in connection with a lamp 
by which a part or all of the rays of light are intercepted and either dif¬ 
fused or reflected or both. This might mean reflectors—either opaque or 
translucent—enclosing globes of diffusing glassware, lenses for redirecting 
the light, or true shades used only for the purpose of shielding the light 
from some particular location. The two latter classes, however, are very 
little used in general and only the two former classes, reflectors and 
enclosing globes, will be given further discussion. 

Reflectors and Their Effect on Efficiency. —“A reflector or shade is 
used in conjunction with a lamp for the purpose of reducing the glare 
otherwise caused by looking directly into the bare lamp, as well as for 
the purpose of redirecting the light most effectively onto the work. 

“Reflectors and shades, both metal and glass, are now obtainable for 
each size of incandescent electric and gas lamp. For a certain ratio 
between the spacing and the height of the lamps, a reflector can nearly 
always be selected w’hich will furnish uniform illumination over the 
working surface.” 

Function of Reflector. —“Owing to the direction of the light from the 
lamp, nearly all types of lamps, in addition to the downward light, furnish 
some rays which go upwards and away in other directions from the objects 
to be illuminated, and are therefore relatively not useful. Furthermore, 
a bright source in the field of vision causes an involuntary contraction of 
the pupil of the eye, which is equivalent to a decrease in illumination inso¬ 
far as the eye is concerned. Hence, while reflectors or shades may at first 
seem to reduce the amount of light in the upper part of the room, their 
use actually increases the amount of light in a downward useful direction, 
and improves the ‘seeing’ due to the better conditions which surround 
the eyes. The economic function of the reflector as contrasted to this 
easier condition it affords the eyes, is to intercept the otherwise useless 
or comparatively, useless rays which do not ordinarily reach the work, 
and to reflect them in a useful direction. In performing this function,' 
there is a choice through the design of the reflector, in the manner of dis¬ 
tributing the light so as to make the illumination on the floor space uni¬ 
form w ith certain spacing distances and mounting heights as previously 
mentioned.” 



LIGHTING IN PLACES OF EMPLOYMENT 


23 


Avoiding Dark Spots. —“With the use of lamps for which a large variety 
of reflectors is available, the proper reflector should therefore be chosen 
so as to give the desired distribution of light. In other cases, as in the 
use of the gas or electric arc lamps, where the globe or reflector is usually 
a fixed part of the lamp, care must be exercised to space the lamps at 
sufficiently close intervals to insure uniformity of the illumination, that 
is, a freedom from the relatively dark spaces which exist between lamps 
when spaced too far apart.” 

Light Interiors. —“With a light ceiling, the reflection of that part of 
the light which passes through a glass reflector to the ceiling, and which 
is added to the light thrown downward from the under surface of the 
reflector, is a factor in building up the intensity of the illumination on 
the working surface. Great importance is therefore attached to light 
interior color, especially on ceilings and the upper portions of walls, both 
in reinforcing the direct illumination, and in giving diffusion, which in 
turn adds to the amount of light received on the side of a piece of work. 
It should also be stated that the intensity of the light from bare overhead 
lamps when measured on the working surface may be increased by as much 
as 60 per cent through the use of efficient reflectors. This is due to the 
utilization of the horizontal rays of light as previously stated, which pre¬ 
dominate in the bare lamps, whereas the most effective light in factory 
and mill work is apt to be that which is directed downward.” 

Points to Consider. —“Reflectors will not be classified here from the 
commercial standpoint, but the following items should be given considera 
tion in the selection of the type of reflector for factory or mill use: 

1. Utilization efficiency: how much does the reflector contribute to 
the effective illumination on the work? 

2. The effect in reducing glare. 

3. Natural deterioration with age through accumulations of dust and 
dirt. 

4. Ease in handling and uniformity of manufacture. 

5. Physical strength and the absence of projections which may increase 
the breakage in case of glass reflectors. 

A study of the various reflectors on the market with the aid of these 
items as a basis wull determine what reflectors are best adapted to given 
conditions.” 


Classes of Reflectors 

Reflectors have become fairly well standardized at the present time 
under a few general classes. 


Opaque 


Steel 


rR.L.M. 

4 Deep Bowl 
[Angle 


Reflectors -< 


Mirrored Glass 


, (Prismatic 

[Translucent j Qpal 

As shown by the tabulation above opaque reflectors are divided into 
two general classes, those constructed of steel and those constructed of 
glass with a mirrored coating over the outside. 





24 


LIGHTING IN PLACES OF EMPLOYMENT 


Steel Reflectors.— The term “steel” lias been used instead of metal 
because it represents the type of reflector rugged enough to he suitable for 
general purposes. These reflectors should be coated on the inside with 
a high grade white porcelain enamel of sufficient density to prevent the 
light from penetrating to the steel body, since the light that reaches the 
steel is practically all absorbed. An aluminum finish is also used in 
some reflectors and in many respects is very satisfactory. However, in 
general the white porcelain enamel reflecting surface will be found to be 
the best. Paint enamel should usually be avoided for reflector surfaces. 
It is difficult to keep clean and in a very short time discolors and cracks 
off. While this type of finish is somewhat cheaper in the first place it 
always proves to be expensive in the end. 

The principal types of steel reflectors are the R.L.M., the deep bowl 
and the angle. 



Deep Bowl Angle Type 

Reflector. Reflector. 

Fig. 3.—Standard Types of Porcelain Enameled Steel Reflectors. 

The R.L.M. is a very suitable reflector with a good distribution of 
light. It is the result of an extensive study and investigation on the part 
of reflector manufacturers and lamp manufacturers, acting through a 
general committee of executive and illuminating engineers in order to 
develop a standard reflector that would improve lighting conditions in 
factories. When this type of reflector is used there should also be used 
either a reflecto-cap or an opal diffusing cap over the bottom of the lamp 
to protect the eye from the direct light of the lamp filament. These 
reflectors are designed for the type “C” (so-called nitrogen) Mazda lamp. 
For the smaller sized lamps the shallow dome gives similar results but in 
general in such cases it is better to resort to the deep bowl type because 
of the better shielding of the light from the eye. 





LIGHTING IN PLACES OF EMPLOYMENT 


25 


The “deep bowl” type is an exceptionally satisfactory type of reflector. 
Its distribution of light is not quite so wide as that of the R.L.M. type and 
its efficiency is slightly less but it provides much better protection to the 
eye, particularly for low mounting and as a usual thing the outlets can he 
located close enough together so as to provide for uniform illumination 
even in such cases. For installations requiring high mounting of lighting 
units, such as over crane ways the deep bowl again has an advantage in 
that its somewhat more concentrated distribution of light places more of 
the light where it can be utilized and wastes less on the side walls. 

“Angle” reflectors are reflectors built for a special service. As a 
usual thing they permit the lamp to be mounted in a normal vertical posi¬ 
tion but direct the light in a general direction towards one side. There 
are many places where they are not only desirable but necessary. For 
example, in erecting shops with high crane ways it is frequently difficult 
to secure sufficient light from the overhead lighting, particularly in the 
vertical plane, i. e., on the side of the work. In such cases angle reflectors 
may be mounted along either side of the crane way beneath the crane 
travel, in this way not only supplying the necessary side illumination but 
also increasing the general illumination along the floor level. 

For local lighting where such is desirable small sized deep bowls and 
angle reflectors are made for either horizontal or vertical mounting. The 
principle, however, is the same as that described in the large reflectors 
above. Another type of reflector for local lighting is the one described 
as a “half shade,” which in general covers the one-half of the light to be 
reflected. Its action is similar to that of the angle reflector. 



Fig. 4 ,—Various Types of Reflectors Suitable for Local Lighting. 


Great care should be taken, however, in the installation of angle reflec¬ 
tors and of local reflectors. They should never be used where workmen 
will have to face them unless they are mounted high enough so as to protect 
the workmen’s eyes from the light. This, of course, can only apply to 
large angle reflectors as it will usually mean a mounting height of not 
less than 20 feet and preferably higher. 

Mirrored Glass Reflectors.—The mirrored glass reflectors are made 
of glass blown into the shape of a reflector, coated on the outside with a 
thin layer of silver and this in turn by a protective coating of enamel. To 
assist in diffusing or breaking up the light so as to avoid any bright 




26 


LIGHTING IN PLACES OF EMPLOYMENT 


streaks appearing on the surface illuminated, the reflector surface is 
corrugated. This is clearly shown in the illustration. These reflectors are 
very efficient and they are largely used for both direct and indirect lighting. 



Fig. 5.—Deep Bowl Mirrored 
Glass Reflector. 



Fig. 6.—Light Distribution Curve 
for Reflector Shown in Fig. 5. 


Prismatic Reflectors. —The “prismatic” reflectors are made of pressed 
glass with the other surface formed of many small prisms. The sides of 
these prisms are constructed in very carefully designed moulds so that 
their surfaces will catch the rays of light at the proper angle to reflect 
them downwards in the right direction. These reflectors are very efficient 



Fig. 7.—Prismatic Reflector. 



Fig. 8.—Light Distribution 
From Reflector Shown 
in Fig. 7. 


Fig. 9.—Prismatic Industrial 
Unit, Giving Wide Distri¬ 
bution of Light. 
























LIGHTING IN PLACES OF EMPLOYMENT 


27 


and afford exceptionally accurate control of the light. For use with 
type “C” (gas-filled) lamps the reflectors should always be covered with 
a white translucent coat for the purpose of breaking up and scattering 
the light to a sufficient extent to eliminate the glaring effect of the 
prisms. Such reflectors are termed “velvet finish.” 

A special industrial type of prismatic reflector shown in the illustration 
is very desirable for installations where an exceptionally wide spread of 
illumination is required, such as in large area lighting. For outside 
lighting, such as yard lighting, a special weatherproof unit is made. 

Translucent Reflectors. —Under translucent reflectors there are two 
general classes, the prismatic and the opal. In distinction from opaque 
reflectors these types permit a portion of the light to escape to the ceiling, 
which in many instances, such as offices, draughting rooms, etc., is a 
very desirable feature. 

Opal Reflectors. —The term “opal” 
is applied to a large class of reflectors. 

They are made of a milky white 
glass and vary through a wide range 
of density. They should be dense 
enough so that it is impossible to dis¬ 
tinguish the location of the lamp fila¬ 
ment or the light source. This results 
in satisfactory diffusion which a lighter 
density could not secure but a greater 
density means an unnecessary absorp¬ 
tion of light usually. These reflectors 
are not so efficient as the prismatic 

and do not control the light so well but Fig. 10. —Deep Bowl Opal Glass 

Reflector 

are pleasing in appearance and are very 

largely used in offices and other places where it is desirable to have some 
light escape to the ceiling and upper walls. 

Enclosing Globes 

The term “enclosing globes or glassware” refers to translucent glass 
globes that entirely enclose the light source. They may be either prismatic 




Fig. 11.—Mazda C 
Enclosing Globe 
Unit. 



Fig. 12.—Mazda C Enclosing Globe 
Unit With Metal Reflector. 












28 


LIGHTING IN PLACES OF EMPLOYMENT 


or opal. The description of these two terms given under translucent 
reflectors is equally applicable here. The opal enclosing globe is used in 
many installations where it is desirable to reduce the brightness of the 
light source. It is very satisfactory in this respect, providing, the proper 
size of globe is selected for the size of lamp used and also providing the 
unit is mounted well above the eye level. 



The opal enclosing globe has no control over the light whatever inso¬ 
far as redirecting it in a downward direction is concerned. The prismatic 
enclosing globe, however, by means of its prisms does control, to a large 
extent, the direction of the light and one class of this form of enclosing 
globe is used for outdoor lighting where a large spread of light is desired 
in the same manner as the prismatic special type industrial reflector or 
band previously described. 



Fig. 15.—Reflecto-cap Diffuser. 















LIGHTING IN PLACES OF EMPLOYMENT 


29 


While enclosing globes are not as efficient as reflectors they offer the 
advantage of the use of clear glass lamps. Bowl frosted lamps should 
always be used with open reflectors, unless reflecto-cap diffusers or opal 
lamp caps are used. 



Fig. 17.—Opal Diffusing 
Cap on Lamp. 


SECTION II—GENERAL REQUIREMENTS 

General Requirements of Artificial Lighting 

“The requirements for good illumination in factories, mills and other 
work places may be summarized as follows: 

1. Sufficient illumination should be provided for each workman irre¬ 
spective of his position on the working space. 

2. The lamps should be properly selected and so installed as to avoid 
or minimize strain on the eyes of the workmen. The type and size should 
be adapted to the particular ceiling height and class of work in question. 

3. The lamps should be operated from sources of supply which will 
insure continuity of service and steadiness of light. 

4. Adequate illumination should be provided from overhead lamps so 
that sharp shadows may be prevented as much as possible, and in such 
measure that individual lamps close to the work may be necessary except 
in special cases. 

5. In addition to the illumination provided by overhead lamps, individual 
lamps should be placed close to the work if they are absolutely necessary, 
and in such cases the lamps should be provided with suitable opaque 
reflectors. 

“These requirements may now be met by means of the new types of 
electric and gas lamps, one type of which can usually be found for prac¬ 
tically each factory and mill location, specially adapted to the general 
physical conditions of the location and character of the work in hand.” 









30 


LIGHTING IN PLACES OF EMPLOYMENT 


Value of Adequate Illumination 

“Factory and mill owners are concerned in the matter of securing the 
largest output for a given manufacturing expense. An improved machine 
tool capable of increasing the product for given labor costs is most attrac¬ 
tive, provided its first cost is within returnable limits out of the larger 
profits. Improved small tools, better methods of handling material, 
adequate crane service, fire protection, good shop floors, accurate and 
efficient timekeeping methods, and similar items, vitally concern the 
shop manager; money is expended to realize excellence in these features 
because they afford increased economies and protection, thus resulting in 
a higher efficiency of the plant.” 

Energy Consumption a Minor Item 

“Many arguments leading to the sale of gas and electric lamps for use 
in factory and mill buildings are based on reducing the lamp operation 
cost by substituting a new for an older system. Arguments of this kind 
are of value, however, only when such a reduction in operation cost can be 
effected without sacrifice in the adequacy of the illumination. It would 
be a poor policy, in the extreme, to argue a saving in energy consumption 
by the substitution of one type of lamp for another on a basis of equal 
candle power in both old and new systems.” 

Effect of Good Light on Production 

“Arguments of a convincing nature, which insure to the factory or mill 
manager an increased output through improved illumination service, are 
of importance and even greater at times than reductions in the cost of 
illumination for the same quantities of light. In view of the fact that 
resulting advantages of superior illumination on increased output are apt 
greatly to exceed economies in operation cost as regards the lighting system, 
it is a distinct advantage to direct and hold the attention on the former 
rather than on the latter. This statement will be more apparent when 
interpreted into definite items as follows: 

Advantages of Good Light.—“While the necessity of good light is so 
evident that a list of its effects may seem commonplace, 4hese same effects 
are of the greatest importance in their relation to factory and mill man¬ 
agement. The effects of good light, both natural and artificial, and of 
bright and cheerful interior surroundings, include the following: 

1. Reduction of accidents. 

2. Greater accuracy in workmanship. 

3. Decreased spoilage of product. 

4. Increased production for the same labor cost. 

5. Less eye strain. 

6 . Better working and living conditions. 

7. Greater contentment of the workmen. 

8 . Better order, cleanliness and neatness in the plant. 

9. Easier supervision of the men. 

In this list it will be noted that items 5, 6, 7, 8 and 9 all have a bearing 
on accident prevention.” 

Interpreting the Advantages of Good Light.—“While the major con¬ 
sideration in the eyes of the factory or mill owner is undoubtedly and 
quite naturally the money value of good light in the larger return of both 



LIGHTING IN PLACES OF EMPLOYMENT 


31 


quantity and quality of work which may result from the installation of a 
superior as compared with an inferior lighting system, it should be noted 
that it is very difficult to interpret into dollars and cents the value of 
good light made possible by such returns. This difficulty is due to the 
necessity of keeping all conditions in a factory or mill section absolutely 
constant while varying the amount of illumination from poor to good con¬ 
ditions, in an effort to determine the output and its dependency on the 
lighting facilities. As accurate data become available, giving the increases 
in production for certain specific improvements in artificial lighting, it 
will doubtless prove helpful to a proper, interpretation of adequate light 
and its worth to any plant.” 

Practical Example. —“Continuing from the manufacturer’s point of view, 
it may be said that certain assumptions as to energy cost, cleaning, interest 
and depreciation, show that the annual operation and maintenance cost 
for the illumination of a typical shop bay of 640 sq. ft. area, may be taken 
at $50.00. If five workmen are employed in such a bay at an average 
wage of say 25 cents per hour, the gross wages of the men in such a bay, 
plus the cost of superintendence and indirect shop expense, may equal 
from $5,000.00 to $7,000.00 per annum. In a case of this kind, therefore, 
the lighting will cost from 7/10 to 1 per cent of the wages, or the equiva¬ 
lent of less than four to six minutes per day. We may roughly say that 
a poor lighting system will cost at least one-half this amount (sometimes 
even more through the use of inefficient lamps and a poor arrangement of 
lamps), or the equivalent of say two to three minutes per day. Nearly all 
factories and mills have at least some artificial light, hence, in general, if 
good light enables a man to do better or more work to the extent of from 
two to three minutes per day, the installation of good lighting will easily 
pay for the difference between good and bad light, through the time saved 
for the workmen.” 

Actual Losses. —“Superintendents have stated in actual instances, that 
due to poor light their workmen have lost much time, sometimes as much 
as from one to two hours per day on certain days. If good light will 
add an average of say one-half an hour per day to the output, these 30 
additional effective minutes represent an increase in output of 5 per cent, 
brought about through an expenditure equal to one-half of 1 per cent of 
the wages for improved lighting, or a saving equal to ten times the expense.” 


SECTION III—NATURAL LIGHT (DAYLIGHT) 

“Adequate daylight facilities through large window areas together with 
light, cheerful surroundings, are highly desirable and necessary features in 
every work place, and they should be supplied through the necessary 
channels not only from the humane standpoint, but also from the point of 
view of maximum plant efficiency.” 

Importance of Daylight. —“The unusual attention to gas and electric 
lighting in factories, mills and other work places during the past few 
years; the perfection of various lamps and auxiliaries by means of which 
an improved quality and quantity of lighting effects are obtained; and 
the care which has been devoted to increasing the efficiency in various 
industrial operations; all go to emphasize the many advantages and 



32 


LIGHTING IN PLACES OF EMPLOYMENT 


economies that result from suitable and adequate window space as a means 
for daylight in the proper quantities and in the right directions during 
those portions of the day when it is available.” 

Three Considerations. —“Three important considerations of any lighting 
method are sufficiency, continuity and diffusion. With respect to the 
daylight illumination of interiors, sufficiency demands adequate window 
area; continuity requires (a) large enough window area for use on reason¬ 
ably dark days, (b) means for reducing the illumination when excessive 
due to direct sunshine, and (c) supplementary lighting equipment for use 
on particularly dark days and especially towards the close of winter days; 
diffusion demands interior decorations that are as light in color as prac¬ 
ticable for ceilings and upper portions of walls and of a dull or mat 
finish in order that the light which enters the windows or that which is 
produced by lamps, may not be absorbed and lost on the first object that 
it strikes, but that it may be returned by reflection and thus be used over 
and over again. Diffusion also requires that the various sources of light, 
whether windows, skylights or lamps, be well distributed about the space 
to be lighted. Light colored surroundings as here suggested result in 
marked economy, but their main object is perhaps not so much economy 
as to obtain a result that will be satisfactory to the human eye.” 

Requirements. —“The following requirements may now be listed for 
natural lighting: 

1. The light should be adequate for each employe. 

2. The windows should be so spaced and located that daylight conditions 
are fairly uniform over the working area. 

3. The intensities of daylight should be such that artificial light will 
be required only during those portions of the day when it would naturally 
be considered necessary. 

4. The windows should provide a quality of daylight which will avoid 
a glare due to the sun’s rays and light from the sky shining directly into 
the eye or where this does not prove to be the case at all parts of the day, 
window shades or other means should be available to make this end 
possible. 

5. Ceilings, and upper portions of walls should be maintained a light 
color to increase the effectiveness of the lighting facilities from window 
areas. The lower portions of walls should be somewhat darker in tone 
to render the lighting restful for the eye. Factory green or other medium 
colors may be used to good effect.” 

Classification. —“Means for natural lighting may be classed under three 
broad divisions as follows: 

(a) That case in which the windows are located on the sides of the 
building or in the framework of saw-tooth construction, where diffused 
light from sky reaches the work during a large portion of the day. 

(b) That case in which windows are located overhead on a horizontal 
or nearly horizontal plane in the form of skylights, thus furnishing direct 
light from the sky during a large portion of the day. 

(c) That case in which prismatic glass takes up the direct light from 
the sky and redirects it into the working space. 

Method (a) is, of course, the most common of the three, and it may be 
noted that the saw-tooth or other roof lighting constructions have become 




LIGHTING IN PLACES OF EMPLOYMENT 


33 


very popular and result in an excellent quality and quantity of light for 
given window areas provided the size and location of windows are in 
accord with modern practice.” 

Increasing the Value of Floor Space. —“Adequate and well distributed 
natural light means that certain portions of the floor space which 
ordinarily would not be available for work, are converted into valuable 
manufacturing space. In a general way, therefore, the average factory, 
mill or other work place, if properly designed should possess natural light¬ 
ing facilities which produce the best practicable distribution of daylight 
illumination.” 

Wide Aisles. —“With low ceilings and very wide aisles, workmen located 
at the central portion of the building must sometimes depend for their 
natural light on windows located at a considerable distance away from 
their working position. In these cases it may be impossible, in general, 
to depend altogether on daylight over an entire floor space, even at those 
times of the day when daylight conditions would be entirely adequate 
under other circumstances. This statement applies to side windows rather 
than to skylights or to saw-tooth construction. Fig. 18 illustrates this 
feature.” 



Fig. 18.—Diagram of a Large Office, 

With Windows on One Side Only. 

Varying Conditions. —“In a case of this kind, employes located next to 
the windows are furnished with suitable daylight in the early morning 
and towards the latter part of the afternoon, the upper portions of the 
windows being particularly serviceable in lighting areas at some distance 
away from the windows. A southern exposure, however, results in such 
excessive light from the sky during the middle of the day, that heavy 
shades are nearly always pulled down so as to cover the entire window 














































34 


LIGHTING IN PLACES OF EMPLOYMENT 


area. This plan makes it necessary to use artificial light throughout the 
larger part of the office during the brightest portion of the day and 
reduces the daylight at those points where it would supposedly be the 
best, namely, near the windows. Here the location of the windows is a 
large factor in the excellence of the daylight conditions but the manipula¬ 
tion of the shades is perhaps even more important. To avoid such a 
difficulty, adjustable translucent upper window shades with adjustable 
opaque lower shades might be employed.” 

Upper Portions of Windows.— “It should be further noted in this illus¬ 
tration that the upper portions of the windows give a reduced illumination 
in proportion to their areas, to the floor space near them. In rooms of 
moderate size, therefore, the windows should be placed as near the ceiling 
as practicable. When the sun shines through windows so located, the 
direct light must be reduced or diffused. This may be accomplished by 
the use of ribbed glass in ordinary factory and mill buildings, and in 
offices by the use of translucent sunshades or awnings.” 

Tempering the Light. — “The light due to the sunshine on such shades 
and awnings will be as bright as ordinary skylight if the shade is well 
chosen, and the ribbed glass will be still brighter. If the windows are 
large, the illumination is likely to be too great near the windows as 
previously pointed out and it must be reduced. This should not be done, 
however, by pulling down an opaque shade over the top of the windows 
because the top portion of the window is the part that is particularly 
needed to give light to the interior of the room. The better scheme is to 
employ an opaque shade which should be raised from the bottom of the 
window. This will reduce the illumination near the window without 
affecting it over the interior of the room to any marked degree.” 


//////// ////// 
CEILING- 



-|- 70 '-- 


BENCH SURFACE-- - .ASSEMBLY WORK; 


!/////////// //h) )////'"'/;/// 7 
ELEVATION 


'-BENCH 


,! 7 


-+-F 


ll l 


'-BENCH'. I 



23 


)////////// 7777777 ?\ 


a 


77777777777 
PLAN 


Fig. 19.—Diagram Showing Benches Located 
With Respect to the Windows So As to 
Receive the Natural Light Most 
Advantageously. 



Bench Location. —“Side windows set a certain limitation upon the 
possible arrangement of the work over the floor space. 

“Two methods of installing benches are in use: (1) In long lengths 
parallel to the windows; (2) in short lengths perpendicular to the windows. 
The first method has a number of disadvantages and hence is now less 
commonly used. 





























LIGHTING IN PLACES OF EMPLOYMENT 


35 


“With benches parallel to the windows, the illumination is non-uniform. 
At points opposite the wall spaces, the illumination may be but one-third 
as high as at points opposite windows. Workmen facing the windows are 
subject to glare from the glass area, and those facing in the opposite 
direction are in their own light. Benches at some distance from the window 
are apt to be insufficiently illuminated. 

“With benches perpendicular to the windows, as in Fig. 19, glare and 
shadow effects are practically eliminated. Although the illumination drops 
off rapidly toward the farther end of the bench, it will be entirely sufficient 
if the benches are not made too long.”—(Industrial Lighting Code of 
Wisconsin.) 

Window Glasses. —“Both translucent and clear glass are employed for 
factory and mill windows. There is a slight reduction in the transmitted 
light through ordinary translucent wire glass, but it is often required by 
insurance regulations for a deduction in the fire risk where a given 
building is located in close proximity to other buildings. Wire glass is 
also used quite generally with steel window frames, here being an added 
protection from the standpoint of fire risk. Wire glass may be obtained 
in clear form, but its expense in contrast to the translucent form is such 
as ordinarily to prohibit its use for industrial purposes.” 

Wire Glass.—“Wire glass, also known as ribbed glass, should be used 
and is advocated for practically all factory and mill windows where 
prisms are not required. Wires of rather open mesh cause so little 
reduction in light as to warrant no mention of this feature. Special care 
should be taken to get such glass as is smooth both on the flat side and 
on the ribbed side to facilitate cleaning. Wire or ribbed glass gives better 
diffusion than plain glass.” 

Prism Glass. —“Where the sky outside of the windows is obstructed by 
buildings, prism glass is recommended if the room is deep. Different kinds 
of prisms can not be used to advantage interchangeably. The amount of 
prism glass required in any case depends much upon the surroundings 
and to obtain excellent results, of which such glass is capable, it must be 
used intelligently.” 

Skylights. —“Skylights are sometimes installed in long narrow continu¬ 
ous strips in a sloping roof. The ribs of the ribbed glass are generally so 
arranged that it is convenient to make them at right angles to the length 
of the strips. The result is that the sunshine is diffused by the ribs 
over a narrow area parallel to the strip of skylight, thus lighting one part 
of the room much more brilliantly than the remainder. If the ribs are 
installed to run parallel to the strips, they will give a much more general 
distribution of the sunlight. In the foregoing the word strip refers to the 
long belt of skylight and not to the individual sheet of glass. Ribbed 
glass in vertical windows should generally be placed with the ribs 
horizontal. They thus roughly fulfill some of the functions or prisms.” 

Monitor Construction (Skylights). —“A better method of getting suffi¬ 
cient natural illumination in the center area of a broad mill is by the use of 
the so-called monitor. This type of construction is shown in Figs. 20, 21 and 
22. To make this method most effective, the ceilings and upper walls must 
be finished white. The light entering the monitor windows will then be 



36 


LIGHTING IN PLACES OF EMPLOYMENT 





Fig. 22.—Two Small Monitors. 






















































































LIGHTING IN PLACES OF EMPLOYMENT 


37 


reflected and diffused from these surfaces, greatly improving the quality 
and intensity of the illumination at the work.” 

Saw-tooth Construction (Skylights.) —“The best method of supplying a 
factory or mill with natural illumination is by means of the saw-tooth 
skylight. With this construction, a nearly uniform intensity and excellent 
diffusion of illumination is secured throughout the work space. It is more 
adaptable for lighting large floor areas in wide buildings with low head- 
room than the monitor skylight. The construction is illustrated in Fig. 23. 
Since the windows of the saw-tooth are faced north or as nearly so as 
possible, the direct rays of the sun are excluded. For this reason saw¬ 
tooth skylights are sometimes called north skylights. The saw-tooth 
skylight is especially adapted to weaving and textile processes, machine 
shops, foundries doing light work, assembling, drafting, and to some dye 
houses where careful color matching is done. 



“As stated, the windows of the saw-tooth must face north; the ribbed 
glass should be inclined to the vertical, to take in a larger sky angle, take 
advantage of the brighter light of the upper sky, prevent cutting off the 
light by the saw-tooth immediately in front, and deliver more light directly 
to the floor; the interior surfaces of the saw-tooth should be painted white 
to intensify and diffuse the illumination at the work. The glass angle 
should be from 20 to 30 degrees from the vertical, and the angle at the 
peak of the saw-tooth should be approximately 90 degrees. 

“Since the windows of the saw-tooth face north, window shades will 
scarcely ever be required if ribbed glass is used. An exception to this 
may be the office. The illumination of vertical surfaces facing toward 
the windows of the saw-tooth will be higher than the illumination on 
vertical surfaces facing in the opposite direction. Hence where strong 
vertical light is necessary, the work should be arranged accordingly. The 
horizontal illumination practically speaking is uniform.”—(Industrial 
Lighting Code of Wisconsin.) 



















38 


LIGHTING IN PLACES OF EMPLOYMENT 


Dirt Accumulations— “While translucent wire or ribbed glass reduces 
the amount of light transmitted through the windows, the roughness of 
the outside surface of such glass often causes accumulations of dust and 
dirt, which are more to blame for the reduction of transmitted light in 
some cases than the translucent nature of the glass itself. Remedies, of this 
difficulty are to secure smooth glass and to resort to frequent cleaning.” 

Wire Glass As a Safeguard— “Wire glass for skylights is, of course, a 
practical necessity as a safeguard against accidents due to accidental 
breakage of the glass or due to objects falling on top of the glass.” 

Sunshine Not Desirable— “In all the work of providing natural light, 
it should be kept in mind that direct sunshine in itself, from the illumina¬ 
tion standpoint but irrespective of sanitary conditions, is not wanted. 
The idea that sunshine is the important item is a common but an erroneous 
impression. For example, in saw-tooth construction, the windows do not 
face the south to get all the sunshine possible, but they face the north 
to exclude the sunshine. Ordinary windows, on the other hand, face all 
directions because not enough light can be distributed to interiors from 
north windows alone. Windows on other than north fronts admit sunshine 
to be sure, and this makes sun shades and awnings necessary to exclude 
the excessive brightness.” 

SECTION IV—ARTIFICIAL LIGHT 

Old and New Lamps. —“The inadequate means available for illumination 
by artificial methpds in the past have contributed to the slowness of an 
appreciation of the features of artificial light which influence the working 
efficiency of the eye. Open flame gas burners, carbon incandescent and 
arc lamps, practically the only illuminants available ten years or so ago, 
play but a small part in the present approved methods of factory and 
mill lighting.” 

New Lamps. —“The large variety of comparatively new lamps available 
for factory and mill lighting includes the merchry vapor, metalized filament, 
tungsten, gas filled tungsten, metallic flame or magnetite arc, the flame 
carbon arc, the quartz mercury vapor, and various types of gas arc lamps. 
Remarkable improvements have thus been made in both the electric and 
gas lighting fields, the same general rules of applying the lamps covering 
both of these fields. Possibilities in factory and mill lighting are now 
attainable which, before the introduction of these new lamps, were either 
unthought of or impossible. Consideration of the eye as a delicate organ, 
together with the new ideas of the items which affect its comfort and 
efficiency, have resulted in establishing certain principles in illumination 
work, and have directed attention naturally and in a growing manner to 
the proper use and application of these new lamps.” 

Lighting Intensities. —“It should be clearly understood that the minimum 
permissible intensity values as required by the Commissioner of Labor 
represent merely enough light to prevent accidents, not in most cases, 
however, enough to prevent injury to eyesight nor to be valuable for 
manufacturing purposes. In almost all cases nothing less than the recom¬ 
mended values as shown in the table in a parallel column with the minimum 
permissible values should be used and in the majority of cases much 
higher values have proven to be very profitable.” 



LIGHTING IN PLACES OF EMPLOYMENT 


89 


Effects on Factory and Mill Lighting Produced by Modem Lamps.— 

“With the introduction of these new gas and electric lamps broader possi¬ 
bilities have been presented in factory and mill lighting. The use of 
units of sizes adapted to the purposes, allows results which it has been 
hitherto impossible to obtain satisfactorily, either by the arc lamp, carbon 
filament or open flame gas burner, formerly available.” 

New Possibilities.—“It is evident that the introduction of the many new 
lamps has made possible what may be termed a new era in industrial 
illumination, a distinctive feature of which is the scientific installation 
of the lighting units; suiting each to the location and class of work for 
which it is best adapted. Before the availability in recent years of medium 
sized gas and electric units the choice of the size of unit for a given 
location was often no choice at all. In many cases, due to small clearance 
between cranes and ceilings, or other conditions making it necessary to 
mount the lamps very high above the floor, but one size or type of unit 
was available, the carbon filament or open flame gas burner in the 
former, and the arc lamp in the latter case.” 






























40 


LIGHTING IN PLACES OF EMPLOYMENT 


Low Ceilings.— “For low ceilings, up to 18 feet, the use either of carbon 
filament, open flame gas burner, or arc lamps resulted usually in anything 
but uniform light over the working plane, and often produced merely a 
low general light which was practically useless for the individual machine. 
In such instances, individual lamps had to be placed over and close to 
the machines. With this arrangement, relatively small areas are lighted 
by each lamp, and the metal shades usually employed, served only to 
accentuate the ‘spot lighting’ effect. Such a form of illumination for 
factory and mill work is unsatisfactory and inefficient, but as stated, 
was in the past, in many cases, the only available scheme. The absence 
of lamps of the proper size is no longer an excuse for the existence of? 
such conditions in industrial plants.” 



PL/\N 


Fig. 25.—This shows a very 
poor arrangement of artificial 
lighting by means of large lamps 
mounted too close to the floor. 
Compare this poor lighting 
scheme with the improved plan 
in Fig. 26. 



Fig. 26.—This illustration is to 
1 e compared with Fig. 25. It 
Rentes an improved scheme 
:r that shown in Fig. 25, made 
ssible by the use of smaller 
imps. 


Determination of Size of Lamp to Be Used.—In order that the engineer 
may be enabled to determine approximately whether he has lamps of the 
proper capacity and whether they are spaced properly the following 
discussion will be given: 

The first thing is to determine the type of installation that will be 
used if this is a new building or an old building which is to be rewired. 
There are three methods of lighting of industrial plants, the geueral 
lighting, local lighting and localized general lighting. In the case of 
general lighting the lighting units are spaced as uniformly as possible 
throughout the building, and mounted high so as to give good illumination 
throughout the factory space. In the case of local lighting the lamps are 
placed low over the machine or work for which they are used exclusively. 
In this case, in accordance with the rules, it is necessary that a few lights 
be hung near the ceiling so as to give general lighting. In the third case, 
the localized general lighting system, the outlets are of large capacity and 
are hung high but are located directly over the machine or the special 


































































LIGHTING IN PLACES OF EMPLOYMENT 


41 




z 

l 

CL 


oo 

bi 



These three illustrations show various was^s in which a factory with 16-ft. girder clearance can be handled, depending on 
the class of work performed. The first class, Fig. 27, is fairly satisfactory for storage spaces, and either the second or third case, 
Fig. 2 8 or Fig. 29, can be employed for bench assembly or manufacturing. The third case, Fig. 29, is to be preferred where the 
class of work consists of the handling of small machinery parts. 







































































































Width of Lighting Bay in Feet as Determined from Fig. 30. 


42 


LIGHTING IN PLACES OF; EMPLOYMENT 




Fig. 31.—Number of Lighting Outlets in Each Row Lengthwise of the Room. 


































































































































































































LIGHTING IN PEACES OF EMPLOYMENT 43 


work in question without regard to any symmetry of arrangement through¬ 
out the room. In this way they concentrate their light upon the work 
desired at the same time giving a general lighting throughout the factory 
space. General lighting should be used wherever possible, although localized 
general lighting is very satisfactory and there are cases in which it 
probably should be adopted. Local lighting, however, is very seldom 
satisfactory and should be avoided. 

Assuming that general lighting is adopted the determination of the 
spacing of the lighting units is the next consideration. Referring to the 
curves in Fig. 30, entitled “Number of Lighting Outlets Across Width of 
Room,” run up the vertical scale on the left of the curve sheet until the 
height of the room is located, then horizontally to the right until directly 
above the width of the room in feet. The point so located will fall in 
some of the areas indicated there, as for example, assume that the room 
has a ceiling height of 14 feet and that the width of the room is 30 feet, 
selecting the point 14 on the scale at the left, running horizontally to the 
right till the point is reached immediately above 30 on the lower scale, it 
is found that the point falls in the area marked 2 bays, that is 2 lighting 
bays, which would mean 2 lighting units to he used across the width of 
the room. Referring now to Fig. 31, “Number of Lighting Outlets in Each 
Row Lengthwise of the Room,” we can next determine the number of light 
outlets in each row. For example, the width of the room was 30 feet, 
we found that there should be two lighting units across the width of the 
room, which would mean that each lighting unit would cover an area 
15 feet wide. We will assume that the length of the room is 60 feet, 
following up the left-hand scale of the second set of curves we find the 
point indicating 15 feet as the width of the lighting bay, following to 
the right horizontally till a point is reached immediately above 60, the 
length of the room in feet, the point thus found falls in the area indicating 
4 bays or 4 outlets for each row. This, therefore, requires 8 lighting 
outlets in the room. 

The next step will be to determine the illumination necessary for the 
work which is to be carried on in this room. In the appendix at the back 
of the bulletin will be found an extended table of recommended lighting 
intensities. The nature of the work to be done in the factory will 
undoubtedly be found listed in this table or if not work of an entirely 
similar nature will probably appear somewhere in the table. This will 
determine the illumination intensity needed. Now referring to Table II, 
headed “Wattage per Square Foot Necessary for Illumination Intensities,” 
the wattage per square foot for each lighting outlet is easily determined. 
The column at the left indicates the illumination intensities, ranging from 
.02 foot candles to 25 foot candles. The three columns at the right show 
the wattage per square foot necessary for opaque reflectors, translucent 
reflectors and for enclosing globes. After finding in the left-hand column 
the intensity of illumination to be used, it is only necessary to run to 
the right and select the wattage per square foot under the column 
indicating the type of lighting fixture to be used. For example, if the 
lighting intensity is to be 4 foot candles and opaque reflectors are to be 
used, the wattage per square foot will be .6. 



44 


LIGHTING IN PLACES OF EMPLOYMENT 






























































































































































































LIGHTING IN PLACES OF EMPLOYMENT 


45 


TABLE II 

WATTAGE PER SQUARE FOOT REQUIRED WITH DIFFERENT TYPES OF 
REFLECTOR EQUIPMENT TO PRODUCE A GIVEN ILLUMINATION 
INTENSITY. AVERAGE FACTORY, WALLS AND CEILING 


Illumination 

Watts per Sq. Ft. for Following Lamp Equipment 

Intensity in 

Opaque 

Translucent 

Enclosing 

Foot Candles 

Reflectors 

Reflectors 

Globes 

.02 

.003 

.004 

.005 

.05 

.008 

.010 

.013 

.10 

.015 

.020 

.025 

.25 

.038 

.050 

.068 

.50 

.075 

.100 

.125 

.75 

.113 

.150 

.190 

1.00 

.15 

.20 

.25 

1.50 

.23 

.30 

.38 

2.00 

.30 

.40 

.50 

3.00 

.45 

.60 

.75 

4.00 

.60 

.80 

1.00 

5.00 

.75 

1.00 

1.25 

6.00 

.90 

1.20 

1.50 

7.00 

1.05 

1.40 

1.75 

8.00 

1.20 

1.60 

2.00 

10.00 

1.50 

2.00 

2.50 

12.00 

1.80 

2.40 

3.00 

15.00 

2.25 

3.00 

3.75 

20.00 

3.00 

4.00 

5.00 

25.00 

3.75 

5.00 

6.75 


The area of the room 30x60 ft. is 1,800 square feet, there are to be 
8 lighting units, therefore, each unit in a general lighting system, where 
the units are uniformly spaced, will light one-eighth of this area, or 
225 square feet, multiplying this area, 225 square feet by .6, gives a 
necessary wattage of 135. Since the two lamps nearest this value are the 
100 watt lamp and the 150 watt lamp, the selection must be made between 
these two and since the 100 watt lamp would evidently give considerably 
below the required illumination, it is not advisable to use that size lamp. 
The 150 watt lamp should be selected. 

This is one of the simpler cases but a little judgment will enable the 
engineer to check in a general way his installation so as to know whether 
he has approximately the right amount of illumination. 

To determine the proper hanging height for the fixtures refer to 
Fig. 32, which gives hanging heights for direct lighting fixtures. The 
type of reflectors with which the engineer will usually have to work will 
be the “extensive” reflector, so in general the other two curves may be 
ignored. The term “spread in feet” means the distance which the reflector 
must cover. In other words, for general lighting it will be the average 
distance between two lighting outlets. In the problem under consideration 
the distance was 15 feet, finding the value 15 along the horizontal scale 
marked “spread in feet” and running vertically until the curve marked 
“extensive reflector” is met, then horizontally directly to the left, we find 
that the hanging height should be 10 feet, i. e., this indicates the distance 
between the floor and the bottom of the reflector for a uniform distribution 
of light on the average working plane. 


SECTION V.—MEASUREMENT 

For the purpose of this code measurements made by the foot-candle 
meter, manufactured by the National Lamp Works of the General Electric 
Company, will be accepted, as being sufficiently accurate, providing, the 
instrument has been calibrated recently enough to be fairly reliable. 



46 


LIGHTING IN PLACES OF EMPLOYMENT 


Brightness Measurements.—The candle power of the brightest square 
inch of light source, as required by rules 6 and 7 may be measured by 
means of a portable photometer, such as the Sharpe-Millar, the Macbeth 
or similar photometers. An opaque board, with a square or circular hole 
one square inch in area, is placed against the surface of the light source 
in such position that the brightest spot emits light through the hole in 
the board. The board must be of such size as to prevent any other light 
from the source to strike the photometer. The photometer is placed at 
some convenient distance from the unit and read, care being exercised 
to exclude all light from the photometer except that emitted from the hole. 
If the photometer is read at a position of one foot distant from the 
light source, the foot candles observed will also be the candle power. If 
the photometer is two feet distant, the foot candles observed must be 
multiplied by four to obtain the candle power. If three feet, they must 
be multiplied by nine, etc., in accordance with the law of inverse squares. 
Care should be taken to make this distance of some appreciable value. 

SECTION VI.— SHADING OF LAMPS FOR OVERHEAD LIGHTING 

Compliance with rule 6, requiring the shading of lamps for overhead 
lighting is made clear by a study of Fig. 1, page 13. The distance shown in 
the figure are only relative. The lamp and reflector shown in the illus¬ 
tration at the most distant part of the room from the workman are 
mounted seven feet above the eye level and are 28 feet from the workman. 
In accordance with the rule, any visible light source lower than the mount¬ 
ing shown for the distance from the observer as indicated must be 
shielded in such a way that the brightest square inch visible shall not 
exceed 75 candle powder. This would prohibit the use of bare lamps and 
would necessitate the use of reflectors, which would effectually screen 
the lamp filament from view or the use of enclosing glassware of sufficient 
size to reduce the brightness per square inch to the required value. 

In all large interiors with ordinary height ceilings, it is usually impos¬ 
sible to secure a sufficient mounting height to avoid screening the filament 
in some manner. In fact it is doubtful whether it is ever advisable to 
attempt to avoid this screening, even though the mounting height is 
sufficient so that compliance with the rule would not necessitate such 
action. All well designed shallow bowl reflectors, provide screening that 
is not less than 14 degrees, and the deep bowl types provide a still greater 
screening angle. If this limiting angle is 14 degrees or more below the 
horizontal, the lamp filament or mantle is considered to be sufficiently 
screened to protect the eye. Almost any of the commonly used types of 
reflecting glassware, such as prismatic glass and opal glass, will reduce 
the brightness of the light source to that specified in the rule and the 
opaque reflectors, such as porcelain enameled steel and mirrored glass, 
completely screen the light source. 

“While the use of proper reflectors or other suitable accessories is 
mandatory under certain conditions when the lamps are mounted less than 
20 feet above the floor, such accessories should be used even where not 
required by the code for economy’s sake. With a well designed and 
efficient reflector the illumination of the work may be increased as much 
as 60 per cent over what the bare lamp will provide.” 



LIGHTING IN PLACES OF EMPLOYMENT 


47 


Where the principal work is done on polished surfaces, images of the 
lamp in these surfaces prove nearly as distressing as the lamps themselves 
and are much more difficult to avoid. In such circumstances the brightness 
of the lamp in all downward directions should be reduced. In some cases 
bowl frosting the lamps may suffice, whereas in other instances the use 
of thin enclosing glass globes, semi-indirect or totally indirect fixtures 
may be needed in order to produce satisfactory results. 

SECTION VII.—SHADING THE LAMPS FOR LOCAL LIGHTING 

The use of bare lamps for local lighting is absolutely prohibited by 
rule 7. Where local lighting is necessary, the lamps may be protected by 
reflectors, either translucent or opaque. Translucent reflectors must be 
of such density, however, as to reduce the intensity of the brightness per 
square inch to 3 candle power or less. Metal reflectors are preferable 
since they screen the eye absolutely from the light and are not subject 
to breakage. 

The reason for this rule should be clearly evident to anyone, since a 
bright light shining directly in the workman’s eye causes it to focus for 
the bright spot, rather than for the amount of light reflected from his 
work, therefore, making it impossible for him to distinguish his work 
clearly. In addition the glare produced by the bright filament is very 
injurious to the eye. This has already been discussed under glare. If 
the lamp, however, is protected properly by a reflector the light reaching 
the eye of the workman comes only as reflected from the work and 
enables him to see distinctly what he is doing as well as to avoid injury 
to his eyesight. 

The following from the Industrial Lighting Code of Wisconsin very 
aptly states the case: 

“While this rule requires the use of reflectors or shades on local lamps, 
this again is to the advantage of the employer from the economy stand¬ 
point. The reflector intensifies the light directed to the work, which 
means that smaller lamps may be used. Not only are the workman’s eyes 
protected but the stray light which causes the glare is caught up by the 
reflector and utilized where wanted at the work.” In Fig. 4, page 25, several 
types of metal reflectors for local lighting are shown. “The angle type 
should be used for lighting vertical surfaces but should always be fixed 
and in such position that a direct view of the lamp is impossible from 
any working position in shop. The lighting of horizontal surfaces in 
many machine operations may be accomplished by means of one of the 
cone or bowl types of reflectors. 

“As already pointed out local lamps should not be used except where 
nothing else will serve the purpose. The operations in any factory or mill 
which can not be illuminated by means of overhead lighting are few indeed. 
When it is considered that a modern intensity of illumination from an 
overhead system is required in all factories it becomes a better plan to 
intensify the overhead lighting so that the illumination received at the 
work corresponds to ordinary practice as given in rule 4, rather than 
install a system of local lighting. When local lighting must be used for 
a given operation it should be supplementary to the general illumination. 
In other words, its function should be merely to intensify the illumination 
at the work or to give light in a particular direction as may be required.” 



48 


LIGHTING IN PLACES OF EMPLOYMENT 


SECTION VIII.—DISTRIBUTION OF LIGHT ON THE WORK 

The General Lighting System; —Under the discussion of “glare” it was 
pointed out that shadows might be the cause of serious contrast glare. 
One very effective means of preventing this condition is to provide a 
good system of general illumination. This is obtained by mounting the 
lighting units high and equipping them with proper reflectors or enclosing 
glassware. 

In Section IV curves are given showing how* to locate the lighting units 
so as to give uniform illumination. The mounting or hanging heights 
thus determined represent a minimum that will prove satisfactory. Greater 
mounting heights are frequently desirable where it is possible to obtain 
them, as the result will usually be greater diffusion of light and the 
removal of the light source further from the eye of the workman. 

The greatly increased efficiency of modern light sources, together with 
reduced rates for energy, have made the use of general illumination a 
practicable possibility. However, when the nature of the workroom is 
such that it is feasible the ceiling and upper walls should be finished in 
a light color and be kept clean. This aids greatly in improving the 
distribution and intensity of the illumination, furthermore, it reduces the 
contrast resulting from the bright source against the background of ceiling 
or walls. 

The advantages of general lighting over local lighting are many and 
may be summarized as follows: Better distribution of light on the work, 
reduction of glare conditions, absence of shadows and dark spaces, and the 
creation of more cheerful working surroundings. This latter is greatly 
improved also by finishing ceiling and w*alls in a light color. 

Side Light Important In Some Factory and Mill Operations. —“It has 

been customary in many cases to measure the effectiveness of illumination 
in terms of the vertically downward component of the light. This method 
has ignored the value of side components in relation to vertical surfaces 
and openings in the side of the work. It is sometimes more necessary 
to light the side of the machine or the side of a piece of work than the 
horizontal surface. If, then, in designing a factory or mill lighting system, 
the prime object is the production of the greatest amount of downward 
illumination, it may happen that the side component is so small that the 
sides of machinery or of work are inadequately lighted.” 

Two Ways to Secure Side Light. —“Experience indicates that there are 
two general ways in which to secure adequate side lighting. One of these 
methods is to lower the lamps, and the other is to use broader distributing 
reflectors than are called for by the rules which consider uniformity of 
the downward illumination only. Side walls or other reflecting surfaces 
will modify the results. Thus, after the determination of a certain type 
of reflector for producing uniform vertically downward illumination, it 
may be found that more side light is necessary, and this extra side 
component may, as stated, usually be secured by selecting a somewhat more 
distributing reflector. Broader distributing reflectors are apt to result 
in less downward illumination and will sometimes call for larger lamps 
than found necessary by preliminary calculations.” 

Practical Case. —“As an illustration, in a certain lighting system a 
vertically downward intensity of about .3 foot-candles was deemed sufficient 



49 


LIGHTING IN PLACES OF EMPLOYMENT 


for the work involved. Measurements and observations. showed that the 
side light was insufficient. In this particular installation it was found 
necessary to produce a vertically downward intensity of about 5 foot- 
candles on the average in order to secure an intensity of about 2 foot- 
candles on the side of the work, and also to use a somewhat broader 
distributing reflector than at first chosen. Two foot-candles on the sides 
of the work were sufficient in this case where bench work and work in 
the vise on small machine parts were conducted.” 

Keeping the Lamps High. —“It is recommended that the lamps be 
mounted near the ceiling in all reasonable cases where side light is 
necessary, and that the side light be* increased, not by lowering the lamps, 
but through the medium of broader distributing reflectors and larger 
lamps, if required. This attitude is taken on account of the glare which 
results when lamps are mounted too close to the work, a feature most 
noticeable in the absence of a reflector or where glass reflectors are used.” 

SECTION IX.—EMERGENCY LIGHTING 

It is of such great importance to make provision against the rooms 
becoming dark at the time of great emergency, like a fire, explosion, or 
some other catastrophe, that emergency lights have been required in order 
that some light will remain on at such times and to provide a means 
for assisting the occupants of the room to escape in the least possible time 
and with the least amount of danger. The location of the rooms, the 
number and types of machines, and the number of employes in the rooms 
determine naturally the relative importance of such system of lighting. 
A room containing a large number of machines and filled with employes 
during working hours would of necessity require a more elaborate system 
of emergency light than one on a ground floor with plenty of opportunities 
for exit and with only a comparatively few workmen. Moreover, the 
system of emergency lighting which would be required in the former case 
would be entirely too expensive for the latter, so that care must naturally 
be exercised in determining what shall constitute the necessary amount 
of emergency lighting. 

Since the importance of emergency lighting is so great, it is necessary 
that the supply to these lights shall come, where possible, from a source 
independent of that which supplies the general lighting for the building. 
Where this is not possible the emergency lighting circuits shall be taken 
from a point on the street side of all service equipment for the main 
lighting supply. 

SECTION X.—SWITCHING AND CONTROL APPARATUS 

It is the intention of rule 10 to have sufficient light located about the 
building so as to enable the watchman to find his way about the rooms 
and to note at a glance whether general conditions are satisfactory or not 
without the need of carrying a lantern. It should be possible, generally, 
for the watchman to turn on these night lights as he enters any main 
room of the factory or workshop, pass through the room and switch them 
off again at the other side as he leaves. The switches controlling the 
night or pilot lights and also the emergency lights must be plainly labeled 
and must be so located as to be readily accessible. 



50 


LIGHTING IN PLACES OF EMPLOYMENT 


The discussion following pertains to the control of lamps and arrange¬ 
ment of switches for general lighting purposes but no requirements have 
been made in the rules relative to this control: 

Control of Lamps and Arrangement of Switches. —“The control of lamps 
in factory and mill lighting is important in all cases, but specially so 
where a large number of lamps is used in preference to a small number 
for a given floor area. For exemple, where an overhead system of 
tungsten lamps of small size is used, a large number will, of course, be 
necessary for a given floor area, and in such cases the number of control 
circuits may at times seem excessive when planned out for sufficient 
flexibility of operation. Such circuits, however, in rendering the system 
more flexible, will be more than paid for by the saving in energy and 
maintenance due to the turning out of lamps not needed in certain sections 
of the factory or mill, provided the number of hours per day during which 
the lamps are used on the average is relatively large, and the differences 
in daylight intensities over the floor area is also relatively large.” 

Control Parallel to Windows.— “The lamps most distant from the win¬ 
dows will usually be required at times when the natural light near the 
windows is entirely adequate, thus making it an advantage to arrange the 
groups of lamps in circuits parallel to the windows. The advantage of this 
method is further apparent when it is considered that if the lamps are 
controlled in rows perpendicular to the windows, all lamps in a row will 
necessarily be on at one time, while a portion only may be required.” 

Practical Case.— “The foregoing statement may be developed into a 
definite proposition. Thus, to install a single switch may involve say $5 
as its first cost. If ten lamps are to be controlled from a single switch, 
these, ten lamps must obviously either all be turned off at a time or all 
turned on, at a time. An additional switch at a cost of $5 will permit 
either half of these ten lamps being turned off, if not required at certain 
times when the remaining five are needed. This extra switch may or 
may not be an economy. Consider, for example, the case where these 
five lamps are of the 60-watt tungsten type, and that they are turned off 
by the extra switch on an average of one-half hour per day while the 
others are needed, or vice versa. In a year’s time, the energy saved at 
1 cent per kilowatt hour, will amount to perhaps 50 cents. At this rate 
it will require ten years for the energy saved to pay for the first cost 
of the extra switch. This would not be considered a distinct economy. 
If, however, the energy cost be greater, and more nearly the average under 
actual conditions, or if the number of hours per day during which a 
portion only of the lamps will not be used, be greater, then these values 
will be correspondingly modified.” 

Locating Switches and Controls— “In locating switches or controls in 
factory and mill aisles, care should be exercised to arrange them syste¬ 
matically, that is, on columns situated on the same side of the aisle and 
on the same relative side of each column. This plan materially simplifies 
the finding of switches or controls, by those responsible for turning on 
and off the lamps, and is particularly important where a given floor space 
is illuminated by a large number of small or medium sized lamps dis¬ 
tributed uniformly over the ceiling area, a feature which is usually 
accompanied by the use of a relatively large number of switches or 
controls.” 




LIGHTING IN PLACES OF EMPLOYMENT 


51 


SECTION XI.—MAINTENANCE 

Windows.—“Factory and mill windows become covered in time with dirt, 
and produce greatly decreased values of natural light in consequence. 
These losses may easily be great enough to affect the workmen seriously 
and to necessitate the use of artificial light at times when otherwise it 
would not be required. Dark surroundings also increase the likelihood of 
accidents. Regular window cleaning should, therefore, be a part of the 
routine of every factory and mill building or group of buildings. See 
Fig. 33. 

Lamps. — “Carbon filament, mercury-vapor, gas mantle and tungsten 
lamps burn out or break, globes and reflectors become soiled, and the 
various other items of deterioration take place so gradually that in many 
cases they are given no special concern in the practical economy of the 
shop. Moreover, it is hardly necessary to mention the fact that often 
lighting systems are allowed to deteriorate to an extreme point and 
nothing is done unless complaints come in from employes after the lighting 
facilities here and there throughout the shop have become so poor that 
work has to be discontinued temporarily. The losses of time from such 
circumstances, when added up throughout a year, are more than likely 
to exceed the expense of, systematic attention to such maintenance items 
in advance.” 

Overhead System. — “Furthermore, with modern methods where the 
lamps are usually mounted overhead rather than close to each machine, the 
importance of relieving the workmen from any care of the lamps, and 
placing it in the hands of a maintenance department is even greater than 
has been the case in the past particularly in large plants.” 

A Method of Inspection and Maintenance. — “In one large factory a regu¬ 
larly developed method of inspection and renewals is employed. As an 
example, the method as applied to several thousand tungsten lamps, which 
are in service in the various buildings, will be described. All the lamps 
are inspected once per day, except Saturday and Sunday. A regular route 
is followed by the inspector, and all burned out lamps, broken switches, 
loose fuses, and similar items are noted. Careful observation is also made 
of reflectors which appear to need washing and any other points which 
might affect the efficiency of the system, after which a report is made up 
about noon and promptly sent to the maintenance department to permit 
all renewals and repairs to be made before night. In this manner the 
lamps are well maintained from day to day.” 

Marking Columns. — “To facilitate this renewal work, it has been found 
advantageous to mark all columns through this shop. The inspector is 
thus enabled to indicate clearly the location of each burned out lamp 
and the renewal man to locate it without delay. It is helpful now and 
then in like manner to have the inspector note the unnecessary lamps 
found burning when artificial light is not required. If lamps are found 
burning at such times, a note sent to the head of the department calling 
attention to the matter, is.usually sufficient to remedy the difficulty.” 

Noting Soiled Reflectors.— “As a check on a regular cleaning schedule, 
the inspector should note all reflectors in need of cleaning. The frequency 
of each cleaning will depend on the rate of deterioration due to the settle¬ 
ment of dirt on the surface of the glass or metal and also on the surface 
of lamps, and the fact should be kept in mind that the amount of dirt 




52 


LIGHTING IN PLACES OF EMPLOYMENT 



Fig. 33.—Curves showing accumulation of dust on fixtures in relatively clean installations. In the aver¬ 
age factory, cleaning would he necessary more frequently than shown by these curves. 
















































































































































53 


LIGHTING IN PLACES OF EMPLOYMENT 

’■ F•/-’ • ””7 - -• ... • .. 

on a reflector is nearly always deceptive, that, is, reflectors which have 
suffered a large ,, deterioration in efficiency due to dirt often appear 
fairly clean, and for this reason it is best to increase the frequency of 
cleaning somewhat over that which seems sufficient from observation, 
particularly in view of the fact that tests indicate large reductions of 
light from apparently small accumulations of dust and dirt. See Fig. 33. 

A Method of Washing.— “In the factory just referred to all reflectors 
are removed to a central washing point. Where the number of reflectors 
to be hauled is large, a truck is used. Often, however, where only a 
small number of reflectors is to be transported, small hand racks, devised 
for the purpose, are employed. When an installation is in need of washing, 
the scheme is to haul sufficient clean reflectors to the location in question. 
The soiled reflectors are then taken down and clean ones immediately put 
into place, after which the soiled reflectors are removed to the central 
washing point, washed and put into stock for the next location.” 

SECTION XII.—CHANGING ■ A POOR INSTALLATION 

“When undertaking the change from an old to a new lighting system, 
the. various forms of illumination which are adapted to factory and mill 
spaces should be studied, and ; an investigation made of the various types 
of gas and electric lamps on the market which are available for the 
purpose. 

“Time should be allowed for a study of the given locations to be lighted* 
for preparing the plans of procedure in the installation of the gas or 
electric lamps and auxiliaries; and for customary delays in the receipt 
of the necessary supplies and accessories to the work in hand. Altogether, 
therefore, work of this kind requires considerable time for its completion.” 

Using the Shop Force.— “In large factories or mills, a wiring or gas 
fitting force is sometimes a part of the maintenance division. The work 
of the wiremen or fitters is likely to be heaviest in the winter due to 
the dark days. Where this condition exists, there is all the more reason 
to apportion out new work so as to accomplish it during the months of 
least wiring and piping repair activity, and further, at that time of the 
year when employes will be comparatively unaffected by the disturbances 
usually associated with a change from an old to a new lighting system 
through possible irregularities in the illumination service while the wiremen 
or fitters are at work.” 

Distribution of Expense. —“Another feature different from the foregoing 
viewpoint is in the distribution of the installation cost over a relatively 
long interval. If, for example, the system is desired for the approaching 
winter, the complete wiring or piping plans may be drawn up and 
blocked out into three, four or even more sections, thus spreading the 
expense over as many months.” 

Yearly Appropriation. —“In some shops a given appropriation may be 
allotted each year for building equipment. From the standpoint of finance 
plans, it may thus be desirable to distribute outlays of this nature over 
the year, rather than to concentrate them at any one time. An important 
consideration in this method of installing lamps, however, is to prepare as 
far as possible the complete plans in advance, at least as regards given 
factory or mill sections, so as to insure a uniform and symmetrical installa¬ 
tion as a whole when the component parts are finished.” 





Fi o- 44 Artificial illumination in one of the large saw mills of the west. 60 and 100 watt Mazda lamps are used in deep bowl, 

porcelain enameled, steel reflectors hung 10 ft. above the floor and approximately 10 ft. apart. 









Fig. 45.—The low ceilings in this trimmer section of a large western saw mill make it essential 
to use low candle power lamps. 40 and 60 watt Mazda B lamps in deep bowl, porcelain 
enameled, steel reflectors (see Fig. 3, p. 24), are hung over the transfer tables, 
giving the maximum light at what might be termed “strategic points.” 











































Pig- 47 —Night lighting on the upper level of a large municipal dock. Four rows of lights run lengthwise of the dock, the two 
outside rows are equipped with 200 watt Mazda C lamps and the two center rows paralleling the center driveway are 
equipped with 400 watt Mazda C lamps. In both cases deep bowl, porcelain enameled, steel reflectors 
are used. The mounting height is 19 ft. above the floor. The wattage per sq. ft. is 0.15. 















































Fig. 48.—A night view of the lower level of the same dock shown in Fig. 47. 100 watt Mazda C lamps in deep bowl, porcelain 

enameled, steel reflectors are hung 11 ft. above the floor with an average spacing of about 25 ft. 


























■ . 



Fig. 49.—Night illumination in a large municipal warehouse. 200 watt Mazda C lamps in deep bowl, porcelain enameled, steel 

reflectors are mounted 20 ft. above the floor and approximately 40 ft. apart. 






































































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Day light illumination by means of monitor construction over the center bay 
and saw-tooth construction over the side bays. 



Day light illumination by means of monitor construction with a series of sky 
lights running transversely in center of building. 































Artificial lighting in an industrial plant using Mazda lamps and prismatic 

reflectors. 



Night view showing mercury-vapor lighting in a low factory section. 






























Day view of a relatively high section, showing a system of gas lighting. 



Well planned system of arc lighting. The lamps are high and above the 

ordinary line of vision. 





















Excessively bad lighting. Bare lamps produce a glare which is harmful and 
renders the illumination very ineffective. 



Very poor arrangement of arc lamps. The lamps are mounted to one side of 
the aisle over the line shafting. Very little light reaches the 
machinery to the right. 























Night view of arc lamp installation with 40 ft. mounting' at center of picture 
and 20 ft. at sides. Excellent distribution. 



Hmh section showing a system of mercury-vapor lamps. Note the excellent 
distribution of light over the floor area. 












































60 


LIGHTING IN PLACES OF EMPLOYMENT 


APPENDIX 


The following table presents the minimum required values as directed 
in the lighting code, together with preferable values for a large class of 
work and is so comprehensive that it is believed that it will include the 


majority of cases that will arise: 

Industrial' Classification 

Assembling: 

Rough assembling . 

Medium assembling . 

Fine assembling ... 

Extra fine assembling .. 


Foot-Candle Intensity 
Minimum 

(Mandatory) Preferable 

1 2 to 6 

2 3 to 9 

3 4 to 12 

5 8 to .... 


Automobile Manufacturing: 

See machine shops, paint shops, wood working shops, etc. 

i • 


Bakeries: 

Mixing and baking .:... 

Boiler, Engine Rooms and Power Houses: 

Boiler rooms .-. 

Coal and ash handling . 

Engine rooms ...—.. 

Auxiliary equipment .. 

Oil switch and transformer rooms . 

Switch boards ... 

Storage battery rooms .—— . 


2 3 to 9 


i/ 2 1 to 3 

1/2 1 to 3 

2 3 to 9 

1 2 to 6 

2 3 to 9 

2 3 to 9 

1 2 to 6 


Brewing, Distilling and Bottling: 

Boiling ...,........ 

Bottling . 

Clearing or resting and fermenting 

Cool ship ... 

Keg washing . 

Keg filling . 


1 2 to 6 

2 3 to 9 

% 1 to 3 

1/2 1 to 3 

2 3 to 9 

2 3 to 9 


Candy Making: 

Cooking over furnaces . 2 3 to 9 

Cooling slabs . 2 3 to 9 

Cream beater machines . 2 3 to 9 

Dipping (hand) .,....... 2 3 to 9. 

Moulding ..........2 3 to 9 

Revolving pan .......... 2 3 to 9 

Spinning bench . 2 3 to 9 ■ 

Weights and measures .. 2 3 to 9 

Wrapping and packing .:.. ..!...... 2 3 to 9 

Canning and Preserving: 

Cooking ...!■. 2 3 to 9 

Assorting, cleaning, cutting and peeling 2 3 to 9 

Hand filling . 2 3 to 9 

Machine filling .. 2 3 to 9 i 

Chemical Works: 

Furnaces 1 2 to 6 

Tanks or cooking, extractors, percolators, nitrators.......... 2 3 to 9 I 

Generators and stills ............... 1 2 to 6 ) 

Drying . y 2 1 to 3 

Evaporators . 1 2 to 6 .* 

Filtration ........;... 1 2 to 6 i 

Grinding: 

Coarse ..:....'..... 1 2 to 6 

Fine .......2. 3 to 9 

Crystallizing .....:.A...1 2 to 6 ; 

Bleaching .. 1 2 to 6 

Electrolytic cells ..'...._2 3 to 9 

Clay Products and Cements: 

Enameling . 2 3 to 9 

Grinding .. .-... i/ 2 1 to 3 i 

Filter press rooms ..,............. r y 2 1 to 3 

Moulding and pressing .. 1 2 to 6 

Cleaning and trimming ... ft . l 2 to 6 

Coloring and glazing .3 4 to 12 

Kiln rooms ... i, ... y 2 1 to 3 

Kiln yards ..’..;.. % to 2 






















































LIGHTING IN PLACES OF EMPLOYMENT 


67 


Industrial Classification 
Cloth Products : 

Cutting . 

Sewing (machine) .. 

Sewing (hand) . 

Pressing . 

Inspecting . 

Cloth treating (oil cloth, etc.) ... 


Foot-Candle Intensity- 
Minimum 


(Mandatory) Preferable 
Light Dark Light Dark 

.. 3 

5 

4 to 12 

8 to .... 

.. 3 

5 

4 to 12 

8 to .... 

.. 3 

5 

4 to 12 

8 to .... 

.. 3 

5 

4 to 12 

8 to .... 

.. 3 

5 

4 to 12 

8 to .... 

.. 2 

3 

3 to 9 

4 to 12 


Construction : 

Indoor . y 2 1 to 3 

Outdoor . X A y 2 to 2 

Dairy Products: 

Separators, evaporators, churns, molds and presses . 2 3 to 9 

Pasteurizing . 2 3 to 9 

Bottle, canning and labeling . 2 3 to 9 

Ice cream freezers . 2 3 to 9 

Draughting Rooms: 

All operations . 5 8 to.... 

Electric Manufacturing: 

Coil and armature winding . 3 4 to 12 

Mica working . 3 4 to 12 

Insulation molding . 3 4 to 12 

Other insulating processes . 3 4 to 12 

Storage battery molding of grids . 2 3 to 9 

Lamp manufacturing .<. 5 8 to .... 

Wire insulating . 3 4 to 12 

Elevators: 

Freight and passenger . y 2 1 to 3 

Forge Shops and Welding: 

Rough forging . 1 2 to 6 

Fine forging . 2 3 to 9 

Drop forging . 2 3 to 9 

Spot and butt welding . 2 3 to 9 

Arc welding . 5 8 to.... 

Foundries: 

Rough molding . 1 2 to 6 

Fine molding ...,. 2 3 to 9 

Core making . 2 3 to 9 

Charging floor . x / 2 1 to 3 

Tumbling . y 2 1 to 3 

Cleaning . 1 2 to 6 

Glass Works: 

Mix room . 1 2 to 6 

Furnace room . 1 2 to 6 

Casting and lehr . 1 2 to 6 

Grinding . 2 3 to 9 

Fine grinding and polishing . 3 4 to 12 

Glass blowing machines . 2 3 to 9 

Cutting glass to size . 2 3 to 9 

Glass cutting (cut glass) ...;. 5 8 to .... 

Beveling . 3 4 to 12 

Silvering . 2 3 to 9 

Inspecting . 5 8 to .... 

Etching and decorating . 3 4 to 12 


Glove Manufacturing: 

Light 

Dark 

Light 

Dark 

Sorting ..... 

. 3 

5 

4 to 12 

8 to .... 

Cutting . 

. 2 

3 

3 to 9 

4 to 12 

Stitching . 

.... 3 

5 

4 to 12 

8 to .... 

Trimming and inspecting. 

.... 3 

5 

4 to 12 

8 to .... 

Pressing ... 

2 

3 

3 to 9 

4 to 12 

Knitting . 

.... 2 

3 

3 to 9 

4 to 12 

Halls, Stairways, Passageways .....- 


• % 

y 2 to 2 

Hat Manufacturing: 

Light 

Dark 

Light 

Dark 

Forming, sizing, pouncing, flanging, finishing, 
and ironing ... 

.... 2 

3 

3 to 9 

4 to .... 

Dveing and stiffening ... 

. 1 

2 

2 to 6 

3 to 9 

Braiding . 

.. .. 1 

2 

2 to 6 

3 to 9 

Cleaning and refining ...-. 

.... 1 

2 

2 to 6 

3 to 9 

Sewing . 

.... 3 

5 

4 to 12 

8 to 12 



























































68 


LIGHTING IN PLACES OF EMPLOYMENT 


Industrial Classification 


Foot-Candle Intensity 
Minimum 

(Mandatory) Preferable 


Ice Manufacturing: 
Ice making .... 


1 2 to 6 


Inspecting: 

Rough inspecting . 

Medium inspecting .-. 

Fine inspecting .. 

Extra fine inspecting .. 

Jewelry and Watch Manufacturing: 

Bench work and extra fine machine work . 

Machine work . 

Stamping .-. 

Engraving . : . 

Jewel working . 

Laundries and Dry Cleaning: 

Sorting and marking .-. 

Washing . 

Mangles and machine ironing . 

Pressing and hand ironing .— 

Dry and steam cleaning . 

Leather Manufacturing: 

Cleaning, tanning and stretching, etc.-. 

Cutting, fleshing and stuffing . 

Finishing and scarfing . 

Vats .-.-.-. 

Leather Working: Light 

Grading and matching . 3 

Cutting and scarfing .-. 3 

Sewing . j* 

Pressing and winding . ^ 

Locker Rooms ...-. 


1 

2 

3 

5 


5 

5 

5 

5 

5 


2 

1 

2 

2 

2 



2 to 6 

3 to 9 

4 to 12 
8 to 


8 to .... 
8 to .... 
8 to .... 
8 to .... 
8 to .... 


3 to 9 

2 to 6 

3 to 9 
3 to 9 
3 to 9 


2 to 6 

3 to 9 

4 to 12 

1 to 3 

Light Dark 
4 to 12 8 to .... 

4 to 12 8 to .... 

4 to 12 8 to .... 

3 to 9 4 to 12 

2 to 6 


Machine Shops : 

Rough bench and machine work .-. 

Medium bench and machine work . 

Fine bench and machine work .-. 

Extra fine bench and machine work ... 

Automatic machines (ordinary) . 

Automatic machines (fine) . 

Grinding, buffing and polishing: 

Rough work .... 

Medium work .-. 

Fine work .-. 

Buffing and Polishing: 

Medium work .-. 

Fine work . 

Meat Packing: 

Slaughtering .— 

Cleaning and cutting . 

Cooking .. 

Grinding and packing . r . 

Canning . 

Milling and Grain Food Products: 

Cleaning . 

Grinding or rolling . 

Baking or roasting . 

Offices . 

Packing: 

Rough . 

Medium .-. 

Fine .-. 

Paint Manufacturing . 

Paint Shops: 

Dipping or spraying ... 

Rubbing . 

Firing .:. 

Hand painting and finishing, ordinary . 

Hand painting and finishing, fine . 

Hand painting and finishing, extra fine (automobile 
bodies, piano cases, etc.) . 


1 

2 

3 

5 

2 

3 

2 

3 

5 


2 

3 


1 

2 

2 

2 

2 

1 

1 

2 

3 


1 

2 

3 

1 


2 

2 

1 

2 

3 

5 


2 to 6 

3 to 9 

4 to 12 
8 to .... 

3 to 9 

4 to 12 

3 to 9 

4 to 12 
8 to .... 


3 to 9 

4 to 12 


2 to 6 

3 to 9 
3 to 9 
3 to 9 
3 to 9 


2 to 6 

2 to 6 

3 to 9 

4 to 12 


2 to 6 

3 to 9 

4 to 12 
2 to 0 


3 to 9 
3 to 9 

2 to 6 

3 to 9 

4 to 12 

8 to .... 


























































LIGHTING IN PLACES OF EMPLOYMENT 


69 


Industrial Classification 

Paper Box Manufacturing: 

Cutting . 

Machine folding . 

Hand folding . 

Pasting and assembling ....... 

Paper Manufacturing: 

Beaters .. 

Calendering . 

Machine . 

Grinding . 

Finishing, cutting and trimming . 

Passage Ways, See Halls. 

Plating: 

Plating .. 

Polishing and burnishing .... 

Printing Industries: 

Linotype and monotype . 

Typesetting ... 

Composing stone .... 

Matrixing and casting ,. t ... 

Miscellaneous machines .... 

Proofreading . 

Presses, job and small automatic .•_.. 

Presses, rotary, flat bed, etc. 

Lithographing . 

Electrotyping ... 

Engraving ... 

Receiving and Shipping . 

Roadways and Yard Thoroughfares . 

Rubber Manufacturing and Products : 

Calendering . 

Grinding . 

Vulcanizing ... 

Washing and compounding rolls . 

Sheet Metal Working: 

Bench work, ordinary ... 

Bench work, fine ... 

Punches, presses, shears, stamps and welders .. 

Spinning .,. 

Miscellaneous machines . 

Shoe Manufacturing: 

Inspecting and sorting raw material .. 

Cutting .. 

Stitching, machine ... 

Lasting and welding . 

Hand turning .... 

Miscellaneous bench and machine work . 

Soap Manufacturing: 

Kettle houses ...... 

Framing . 

Cutting . 

Stamping, wrapping and packing ... 

Soap chip . 

Soap powder .,... 

Filling and packing soap powder . 

Staii'ways, see Halls. 

Steel and Iron Mills, Bar, Sheet and Wire Products : 

Automatic machines . 

Charging floor . 

Casting floor .... 

Soaking pits and reheating furnaces ... 

Muck rolling .. 

Other rolling . 

Shears, presses, punches and riveters .. 

Rod mill ... 

Wire drawing, coarse . 

Wire drawing, fine . 

Pickling and cleaning . 


Foot-Candle Intensity 
Minimum 

(Mandatory) Preferable 
Light Dark Light Dark 

. 1 2 2 to 6 3 to 9 

. 1 2 2 to 6 3 to 9 

. 1 2 2 to .6 3 to 9 

. 1 2 2 to 6 3 to 9 


1 2 to 6 

2 3 to 9 

1 2 to 6 

1 2 to 6 

3 4 to 12 


2 3 to 9 

2 3 to 9 


5 

5 

5 

2 

2 

3 

2 

2 

3 

3 

5 

1 

1-50 


8 to .... 
8 to .... 
8 to .... 
3 to 9 

3 to 9 

4 to 12 
3 to 9 

3 to 9 

4 to 12 
4 to 12 
8 to .... 
2 to 6 

1-20 to *4 


2 3 to 9 

1 2 to 6 

1 2 to 6 

2 3 to 9 


2 3 to 9 

3 4 to 12 

3 4 to 12 

3 4 to 12 

2 3 to 9 


Light 

Dark 

Light 

Dark 

. 3 

5 

4 to 12 

8 to .... 

. 3 

5 

4 to 12 

8 to ... 

. 5 

5 

8 to .... 

8 to .... 

. 3 

3 

4 to 12 

4 to 12 

. 2 

2 

3 to 9 

3 to ^ 

. 2 

3 

3 to 9 

4 to 12 


1 

2 to 6 

% 

1 to 3 

1 

2 to 6 

2 

3 to 9 

1 

2 to 6 

1 

2 to G 

2 

3 to 9 


2 

3 to 9 

% 

1 to 3 

% 

1 to 3 

x / 2 

1 to 3 

1 

2 to 6 

2 

3 to 9 

2 

3 to 9 

2 

3 to 9 

2 

3 to 9 

3 

4 to 12 

1 

2 to 6 




























































70 


LIGHTING IN PLACES OF EMPLOYMENT 


Industrial Classification 
Stone Cutting: 

Machine cutting . 

Hand cutting ... 

Carving . 

Polishing . 

Store anil Stock Rooms: 

Rough storage ... 

Rough stock .. 

Medium stock . 

Structural Steel Fabricating . 

Telegraph: 

Operating . 

Telephone: 

Automatic exchanges . 

Manual exchanges . 

Testing: 

Rough . 

Medium .. 

Fine . 

Extra fine . 

Textile Mills: 

Cotton : 

Opening and lapping .. 

Carding .... 

Drawing frame .. 

Roving, spooling, spinning, etc.. 

Warping ... 

Slashing .. 

Drawing in . 

Weaving . 

Dyeing . 

Silk: 

Winding . 

Throwing . 

Quilling and warping . 

Weaving .....:. 

Dyeing . 

Finishing . 

Woolen: 

Picking . 

Washing and combing . 

Carding . 

Twisting . 

Dyeing . 

Drawing in . 

Warping . . . 

Weaving ... 

Perching . 

Knitting machines, ordinary and nappers 

Knitting machines, flat and others . 

Cordage mills . 

Tobacco Products : 

All operations . 

Toilet and Wash Rooms . 

Wood Working: 

Rough sawing (sawmills) . 

Sizing, planing, rough sanding, etc. 

Machine wood working, medium . 

Machine wood working, fine . 

Bench work, medium . 

Bench work, fine . 

Fine sanding and finishing . 

Gluing and veneering . 

Cooperage . 


Foot-Candle Intensity 
Minimum 

(Mandatory) Preferable 


1 

1 

2 

2 


y 2 

1 

2 
2 


3 


3 

2 


1 

2 

3 

5 


. 1 

. 1 

. 1 

. 2 

. 2 

. 1 

Light Dark 
..2 2 

..2 2 

..2 2 


2 to 6 

2 to 6 

3 to 9 
3 to 9 


1 to 3 

2 to 6 

3 to 9 
3 to 9 


4 to 12 


4 to 12 
3 to 9 


2 to 6 

3 to 9 

4 to 12 
8 to .... 


2 to 6 
2 to 6 

2 to 6 

3 to 9 
2 to 6 
2 to 6 

Light Dark 
3 to 9 3 to 9 

3 to 9 3 to 9 

3 to 9 3 to 9 


O 

. Li 

.... 2 

Light Dark 
..2 3 

..2 3 

..2 2 

..2 3 

. 2 

. 2 

. 1 

. 2 

. 2 


3 to 9 
3 to 9 

Light Dark 
3 to 9 4 to 12 

3 to 9 4 to 12 

3 to 9 3 to 9 

3 to 9 4 to 12 

3 to 9 
3 to 9 

2 to 6 

3 to 9 
3 to 9 


Light 

Dark 

Light 

Dark 

... 2 

3 

3 to 9 

4 to 12 

... 2 

3 

3 to 9 

4 to 12 

... 3 

5 

4 to 12 

8 to .... 

... 5 

5 

2 

3 

8 to .... 

8 to .... 

3 to 9 

4 to 12 


2 3 to 9 

2 3 to 9 

1 2 to 6 


1 2 to 6 

2 3 to 9 

2 3 to 9 

3 4 to 12 

2 3 to 9 

3 4 to 12 

3 4 to 12 

2 3 to 9 

2 3 to 9 


























































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